To the last part, yes, basically. They hate Israel because (this is me summing up a lot of disconnected "ideologies" from them):
-Israel is Jewish. -They hate Jews. -Zionist=Judaism.
Some of them, although all this stuff is very disjointed, believe that Trump is like a "Jewish puppet" (they will sometimes substitute Zionist with the intention of meaning Jewish. They do not distinguish a difference. All Jews are Zionists loyal to Israel to them. Classic antisemitic stuff). His son in law, Jared Kushner, was in charge of a lot of foreign policy stuff in the Middle East including the treaty that was meant to full solidify the alliance and support from the surrounding Arab countries like Saudi Arabia with Israel. This was interrupted by partly 1) Trump losing re-election but mostly 2) recent Palestinian resistance starting on Oct 7 last year. The groypers see this as Kushner, who is Jewish, manipulating Trump or Trump working in cooperation with "the Jews", however they want to frame it, to sell out America to the "the Jews" and "the Arabs." They see America as a place that should be only white people, which apparently now includes Hispanic whites and not just anglo/germanic whites (crazy developments are emerging in Nazi ideology), and has no Jews, they belong in Israel, which the US should have no role in supporting (or killing the Jews outright, again, depending on the relative insanity), no black people, brown skinned Hispanic, Latino, no indigenous, no Asians... you get get gist. Typical Nazi stuff.
But yeah the hangup with them specifically is Trump/US support of Israel and their deep racist hatred of Jews. It's basically like if the racist republicans were fully ideologically consistent in their racism... you get a groyper who wants absolutely nothing to do with Jews or anything even associated with Judaism.
Some of them do hesitantly, lightly support Trump btw. I believe Fuentes has been on record as supporting Trump as sort of a means to an end transitional figure. He said something like "we elect Trump twice and then we have no more elections" like he will form an actual empire, dissolve the republic, Rome style, and then the next person will be a "based anti-Jewish groyper." Or whatever.
Now I must go shower.