The Soviets in Russia saw themselves as being part of something bigger than themselves, and they murdered more people even than the Nazis, who also saw themselves as being a part of something bigger than themselves.
Belief that something beyond your own life matters is really not that hard for anyone to do. Even the pagans will sacrifice their lives for their loved ones. Their family. Their country. Some ideal.
At some point or another, every atheist must grapple with the absurd. How do many deal with it? Not much has changed in the last couple centuries. They decide that they can arbitrarily decide and make life's meaning.
And that is what atheism is to the core. An embrace of arbitrariness. If there is no truth, truth is whatever I make it out to be. Whatever is convenient. Whatever works for me.
But the thing is, in the end, none of this will be fulfilling. The Truth is what liberates oneself from vanity. The Truth is the only salvation from this world of suffering.
Without it, people can go on living their lives constantly entertained and amused by media, eating more in a day than some in the world eat in a week, and living their lives satisfying every impulse and pleasure while saying to themselves, "I'm a good person, and I don't live a hedonistic life. Look, at how they are living, they are the amoral and selfish, not I".
Meanwhile the world outside is falling apart, the love of self is magnified, the love of many is waxing cold, and people through covetousness masquerading as compassion call for the looting and robbing of others to solve all these problems piling up.. problems that are primarily the result of a real spiritual sickness.
And if a real awakening doesn't happen soon, and I mean a mass awakening, people might wake up to find themselves in a land where they are no longer free to abuse the liberty they once geld dear. They may find that what they thought was liberty was in fact slavery to vice, and it was this vice that fooled them into denying the truth. These idols chosen in preference to The Truth will not save, and will lead those seduced by them into perdition.