"Stolen" is ambiguous and those poll questions are poorly worded. It would be hard to extrapolate or generalize from responses, as a result.
But your post sort of touches upon the bigger issue, which is the extent to which disinformation forms the bedrock of the Trump base's political understanding. Deranged conspiracy theories and a paranoia that approaches levels of psychosis has led certain low-information voters to believe demonstrably false and objectively stupid things.
And we all know what they are. I need not list them here.
It's possible that the structure and mechanics of how we communicate have contributed to this to some degree (though I am not sure how precisely that could be measured). Twitter, for example, seems to be a snake's den of misinformation and collective insanity. And politics seem to be downstream from Twitter. So there may be some kind of link there.
But this phenomena is not unique to the populist/movement right wing, either. The difference is that right wing conspiracy theories react to left wing conspiracy theories. Right wing conspiracy theories oppose the sociopolitical and sociocutlural changes that left wing conspiracy theories drive.
There's no shortage of stupid beliefs on the so called "progressive left," either. And in fact, there are groups that appear somewhat comparable at varying levels of analysis (particularly with respect to race, gender and sexuality). Here, too, deranged conspiracy theories and a paranoia that approaches levels of psychosis has led certain low-information voters to believe demonstrably false and objectively stupid things.
The difference is that whereas Q Anon becomes a subject that the media report on as a "conspiracy theory," the media humor most of the more insane things that the progressive left believe without anything even vaguely resembling an evidentiary basis. Those conspiracy theories include, for example, concepts such as the "wage gap" and "systemic racism."
The wage gap conspiracy theory basically claims that women are systematically discriminated against in "the workplace" (the labor market) because of their gender. As evidence of this, they cite misleading figures that have been manipulated into suggesting that women earn about 70 cents or so on the dollar of every man. Further, so called progressives emphasize the "lack of representation" of women among fortune 500 companies, and the like. As if the question of "why are there so few female CEOs of fortune 500 companies?" could be explained by "the patriarchy."
In reality, once you control for individual choices to do things like having children, and the impact that such a choice has on the net life earnings of women, generally; there is no difference. Further, the earning figures in basically every Western country tend to suggest that millennial women out-earn millennial men by at least 20 - 35 percent. And the trend is looking up in that respect, meaning that once you evaluate the relative earning of men and women (even not considering the choice to have children that some women make) women still out-earn men, within certain age groups and will continue to out-pace them for the foreseeable future. This should be unsurprising, given that women have consistently achieved higher levels of educational attainment than men in secondary and post-secondary education for about a decade now.
But somehow the patriarchy is keeping women down? This is stupid.
Conspiracy theories of systemic racism are more pernicious, though. This conspiracy theory basically claims that non-majority groups are discriminated against in "the society" and its levels and iterations based on their race and is so pervasive that it has all but become common knowledge among the media and certain "mainline" groups, like center to progressive left. As evidence of this, they cite misleading figures that suggest that non-congruent outcomes among particular (and largely non-representative) samples of non-majority ethnic groups have it worse than equally non-representative samples of majority ethnic groups.
In reality, to the extent that any such differences appear in the data (and they do in certain aspects, like criminal sentencing for example); there is essentially no evidence that could even be misinterpreted to support the proposition that race (or ethnicity) explains these differences, much less causes them. Further, once you broaden the scope of whatever you're looking at (basically no matter what it is that you're focusing on), at least before 2020 things tended to be looking better compared to, for example, criminal sentencing disparities in the 1930s-1970s. This should be unsurprising, given that as a society racism is regarded as intolerable by basically everyone with any sense, and the cultural norms associated with discriminating based on race have shifted.
Further, if you wanted to look at other factors beyond things like criminal sentencing like black economic advancement, and you compared the relative change in the economic status of black Americans after the end of the civil war to, say, about the Johnson administration, it would be pretty clear that things were definitely looking up. Despite widespread cultural and structural barriers (most of which have since been removed), black Americans profoundly improved their position up until that time. But after 30 years of the welfare-state's expansion and progressive social reforms, and---above all---liberal criminal justice reforms supported by people like Joe Biden (e.g., 94 crime bill) the rate of improvement took a turn for the worse. If the "systemic racism" conspiracy theory was true, then the society should have been more racist after Johnson was elected, and the society's collective racism should have profoundly increased thereafter (if we are going to explain that post-Great Society downward trend by "systemic racism"). There are no data that could even be misinterpreted to support that position.
Despite this, the "systemic racism" conspiracy theory is basically understood as axiomatically true. But it sure looks to me like it's a way for woke (and often white) leftists to exploit black people for their own purposes, even though the most significant collective setbacks to black people generally have been visited upon them by people like Bill Clinton and Joe Biden, in the 1990s.
I am not saying that there were never systemic issues that disproportionately adversely affected black people, if there was any question. Three strikes laws absolutely did, drug sentencing practices relevant to crack certainly did and so called crime reform at the behest of the 1990s democrats did more damage than anything else. But to call these evidence of systemic racism is stupid and myopic. What it suggests is that whenever the government tries to implement policies like this, it makes things far worse than better. Also, sentencing disparities increased after the 94 crime bill. So if the systemic racism theory is true, then democrats bear the responsibility for shaping the current system and its racism for the most part. But if it's not true, then maybe we need to look a bit deeper to understand what is happening rather than repeating stupid things people don't understand on Twitter like AOC.
The bigger question is why do people believe stupid things for which there is no evidence? It seems to me like we have lost the ability to think critically, in favor of reflexive reaction. So like whenever anyone suggests that there is no gender gap, this makes them a sexist. Or whenever anyone suggests that so called systemic racism is more of a political myth used to exploit black people rather than a useful theory through which to understand current social problems, they are automatically a racist.
There are a lot of people that just don't buy that. There are also a lot of people who resent being called a sexist or a racist for having opinions that diverge from whatever woke leftists think is acceptable, but aren't intellectually sophisticated enough to explain why they think the leftist woke approach is acceptable. And when the means by which knowledge is produced is coming up with this garbage, it's the credibility of those institutions behind that process, which is lost.
If the goal was to set up a regime of truth that divided the body politic into warring against itself, then the leftist progressives have done an excellent job. Self-styled experts claim sole and exclusive dominion on not only "what the truth is" but also on "the means by which that which is true can be known." They define what the norm/standard is, and to the extent anyone disagrees they are not only rebuking the current political milieu but the purportedly intellectual foundation upon which that milieu is predicated and the institutions that set up those conditions in the first instance.
Is it any wonder, then, that the low-information right wing have all but totally rejected basically all forms of mainline institutions and retreated into belief in conspiracy theories like Q-anon? When the alternative is to be labeled a white supremacist, racist and sexist bigot? It shouldn't be. Belief in this kind of thing is an act of misguided resistance to a cultural cancer that they intuitively understand is wrong, and to which they will not submit. That's a big part of why Trump was elected, and why someone worse is more likely than not to be the 2024 Republican nominee.