Much like the Pittsburgh synagogue shooter, the Poway synagogue shooter claims to not be a fan of Donald Trump because Trump is supposedly too deep in the pocket of the Jews. From this, Trump's defenders argue that it is a slander to tie Trumpism to the shooting or to associate him with any form of antisemitism whatsoever.
While there certainly is direct antisemitism in Donald Trump's behavior -- mostly centered around "globalists", Soros, and "Sheriff's stars", it is true that Trump in his own words is not aggressively antisemitic at the level he is Islamophobic or xenophobic. This, in my view, is almost purely a matter of familial fortune -- the brand of right-wing politics he promotes goes hand-in-glove with antisemitism, and if his daughter didn't happen to be Jewish, I think we'd see far more explicit forms of antisemitic appeals out of Trump.
One implication of that is that Trumpism, if you will -- the political movement of which Trump is an avatar but ultimately only one member -- is a lot more antisemitic than Trump himself is (to take one example: Ann Coulter). And so it is perfectly compatible for people who are in all relevant respects Trumpist, and who inspired by the political movement Trump help usher into the mainstream, to find Trump himself to have sold them out on "the Jewish question". They know what this movement actually stands for, and they know that Trump is holding back on living it out when it comes to the Jews.
The weird analogy I have might well be to Jon Lansman of Momentum. Momentum is an antisemitic movement. Lansman himself is certainly not good on antisemitism, but he has not personally joined in the sort of direct, vicious antisemitic harassment that has characterized the movement he founded. And because he hasn't -- and because he's Jewish -- many backers of Momentum, the movement, detest Lansman, the movement's titular founder. But it would nonetheless be weird to say that because this or that Momentum-esque antisemite publicly avows that they hate Jon Lansman, that therefore Lansman did not help inaugurate a deeply antisemitic movement in the UK. Of course he did.
And of course Trump did here in America. It is basically a historical accident that Trump is not personally more antisemitic than he is (just as it is a historical accident that Momentum happened to have been founded by a Jew). That accident has an effect -- but not as large of one as you might think. Ultimately, Trumpism is a movement that has done more than anything else to mainstream antisemitic violence as a feature of American Jewish life. The types of conspiracies and tropes and anti-"globalist" paranoia that Trump helps stoke -- aided by Republican allies like Steve King and Mo Brooks and Kevin McCarthy -- maybe doesn't go far enough for antisemitic extremists' tastes. But it definitely helps create the environment where they thrive.
Whether they like Trump or not, they're Trumpists. And Trump should be held squarely responsible for the threats he's created.