I think at least some of it is the extreme, outrageous, unbelievable levels of incompetence from the Israeli propaganda machine. There's a lot more clear evidence of straightforward war crimes coming out of Palestine, and much of that evidence is posted to Twitter by Israeli soldiers. If there was a daily drip feed of, say, Ukrainian soldiers just setting children on fire for fun, I think you'd see a dip in the public support of that war also. Israel was so convinced that they had the unwavering support of the to do whatever they wanted that they really have made no effort to do genuine propaganda or cover up their worst excesses. It turns out that they were right to be convinced of that, since nobody has actually done anything about it, but their laziness has eroded their popular support.

Most of the really awful stuff coming out of Ukraine requires you to be familiar with fascist iconography (the Black Sun, wolfsangel, etc.) to appreciate and find horrifying. In contrast, to be horrified by Israel you only need to have eyes and not be really super racist.