If Israel conquers Palestine and extends voting rights to Palestinians, then Israelis and Palestinians will collectively vote for a central government to decide on laws. If Palestine conquers Israel and extends voting rights to Israelis, then again, the government is collectively decided. Most one-state proponents seem mostly concerned with their country owning land and not as concerned with the logistics of the government, so democracy should be an acceptable compromise if it means they get one state.
So, let's say we combine Israel and Palestine into one democratic nation and let each side call it what they want. Israeli nationalists should support this, because it gives them what they want by another name. Same for many Palestinian nationalists. Achieving this diplomatically could probably ensure a stable government close to the democratic ideal I described above. Two-state proponents want both sides to have national sovereignty, which is achieved if everyone in the combined nation gets to vote.
Right now, this isn't feasible. However, I suspect that is because not much effort or political will is put into solving things this way. Only a quarter of Israelis and 35% of Palestinians support a one-state solution. Most of this seems due to logistics. Demanding that Israelis or Palestinians be guaranteed certain rights, for example. Yet with how much money is being put into military spending, how many missiles are being fired, etc. it seems like it's worth spending more time hammering out a constitution both sides can agree to.
If you're Israeli and don't support a one-state solution, what's your plan to winning against Hamas? It's pretty clear Israel doesn't want to do nothing, but if they conquer Palestine, we're back to the one state idea. If you don't like that Hamas breaks ceasefires, then you should want a unified government that can enforce terms.
If you're Palestinian, support democracy, and believe that "from the river to the sea, Palestine should be free," then isn't one state what you want? Wouldn't it be easier to achieve this through negotiations rather than warfare? Is it worth bombing Israel for decades just to call the country a different word?
Maybe one side wants to conquer the other and exclude them from voting, but I just see that causing more violence. Also, I don't think letting the other side vote would be that destructive anyway. The US even let West Germany and Japan hold elections after World War II.