Two years after the 2005 Israeli unilateral withdrawal from Gaza (and the Israeli government evicted Israeli settlers from Gaza), the support in Israel for a two-state solution was 70% in favor.
They were optimistic!
Looking at the long term history of Israel, the left was more optimistic in general about hopes for peace with the Palestinians, while the right more suspected that Arafat never really wanted peace, and was just being sneaky. But let it be noted that the Prime Minister who ordered the withdrawal from Gaza was right-wing Gen. Ariel Sharon, Likud member and previous advocate of settlements everywhere.
After the actions of Hamas in subsequent years, particularly Oct 7, 2023, that hope and optimism was completely eliminated.
The 'withdrawal' wasn't really a withdrawal, was it. There was still a blockade, and IDF's routine 'mowing the lawn'.
Let's not pretend that the 2005 'withdrawal' was a chance for a fresh start for the Palestinians that they floundered. The various negotiations were very one sided, and the offers were also unacceptable.
Since 2005, Israel has aggressively settled more and more people in the West Bank, to the point where more than 10% of Israel's Jewish population (read: first-class citizens) now live in West Bank settlements, so Israel's right wing has done everything in its power to make a two-state solution less and less practical.
IMO a one-state solution where everyone has equal rights is the only just and reasonable path forward. Like with the dismantling of apartheid, a transition plan will be needed.
Hamas has a one-state transition plan: kill or drive out the Jews, or enslave the ones with technical expertise. The Israel far right has a transition plan: kill or drive out the Palestinians in the West Bank or Gaza, except for the few that don't cause them problems.
Partition of disputed territory is the least bad solution in the world we live in. "One world" government remains a utopian fantasy. Dividing the world up according to a mix of consideration of peoplehood, self-determination, and whoever won the most recent war is what humankind has figured out so far.
People who disagree with that will want to start wars. Wars are bad.
Wars are bad, but sometimes the only way to end an unjust status quo. Is that a defense of war? Up to everyone to decide.
The American civil war occurred, in part, because Lincoln decided to end the institution of slavery. I know this is an oversimplification and justifies the means with the end, but I think if "bad"-ness of the civil war is compared to the "bad"-ness of an eternity of black people being enslavement in the U.S., I'd argue the war was significantly less "bad".
I think your other point about Hamas's supposed desire to genocide Jews lacks nuance, and your resignation to a world of ethno-nationalist states is a just-so story bordering on nihilism, but I suspect addressing those enters territory of tightly-held opinion, so I will just leave it at that.
They were optimistic!
Looking at the long term history of Israel, the left was more optimistic in general about hopes for peace with the Palestinians, while the right more suspected that Arafat never really wanted peace, and was just being sneaky. But let it be noted that the Prime Minister who ordered the withdrawal from Gaza was right-wing Gen. Ariel Sharon, Likud member and previous advocate of settlements everywhere.
After the actions of Hamas in subsequent years, particularly Oct 7, 2023, that hope and optimism was completely eliminated.