I addressed the same point in a sibling comment: https://news.ycombinator.com/item?id=38620617

Basically, I think it comes down to options. After WWII, the average person in Germany or Japan wasn’t forced out of their home and livelihood, and the Marshall plan was quite effective at giving people peaceful options to be proud of. What I’m not seeing now is how Palestinians get something similar, and if you push people into a corner even non-violent people will conclude they have no alternative.

What do we consider "forced out of their home and livelihood".

Allied bombing of Japan in WWII destroyed upwards of 3.4 million homes and rendered the areas unlivable for a period of time.

Consider how that would have gone if we had then moved settlers into that space, including areas we hadn’t formally claimed, and dared the former residents to make us leave. There’s a big difference between “we have to rebuild” and “other people are living well in your fathers’ homes but you live in a squalid camp”.

Kaliningrad/Königsberg is a more apt comparison then? Because that's functionally what the CCCP did.

Actually something like that happened with Kaliningrad after WWII. The German population was forced out and Russian population brought in. The language was changed to Russian.

Definitely, but Kaliningrad had something like 100k people out of a total German population of roughly 80 million? I'm sure plenty of them had grudges but they didn't have an outlet to act on them unless they wanted to sneak through another country on their way to suicidally attack the USSR and, what I think is most important, the alternative was to build a comfortable life in Germany proper, where they were fully integrated with the language, customs, and political system. Grudges don't usually turn into violence, especially with suicidal odds of retaliation, when people have hope. I'm sure there were plenty of old Germans complaining about it – over beers, with full bellies, and going home to warm beds unwilling to do anything which would risk those comforts.

My argument is that Israel needs to figure out how to get to that level for Palestine: if you want peace, you want people to have prosperous farms and businesses to focus their energies on and confidence that if they do so those won't be taken away or destroyed.

Also, areas of Germany were given to Poland and the Soviet Union post WWII and many Germans were displaced.

In this case it’s also complicated by the lead up to the Cold War: I’m sure plenty of Germans resented that but even the ones who would consider violence knew that there was no likelihood of being able to win a military confrontation with the USSR. Attacking an Allied military occupation in Germany would not only have had no direct effect, it might have made things worse if that lead the American army to withdraw and leave the troublemakers to the tender mercies of the Red Army.

Again, my point was that while those countries didn’t have it great, they had peace after brutal wartime conditions and the prospect of rebuilding. Yes, having to flee would be unpleasant but they ended up in another part of their country where they were unquestionably welcome, spoke the language, and were able to participate in the government (which certainly hadn’t been the case for the previous decade for anyone who wasn’t a committed Nazi), and then the victors were rather generous in helping them rebuild.

Many, but not the vast majority, and they still had their homeland(s). That's the crucial difference.