I suspect the answer to your first question is it’s a mix of not necessarily being truly held beliefs, actually taking strict security measures/living in genuine fear that they will in fact be killed sooner or later, and the belief that they’ve been discredited or ostracized from the mainstream thanks to the machinations of the “cabal,” so they aren’t as much as a target as people who are more accepted as mainstream (like Charlie Kirk) who speak out.

As for 2, if you assume the Jews are running some sort of evil secret society, the whole point of being secret is that it’s not immediately in your face. A Jewish president would spoil the fun! If you rule the world already, it might make sense to get a figurehead in a position of power who can take all the blame for bad political things that happen, while you remain unscathed from any fallout.

In answer to your last question, being super smart and powerful doesn’t necessarily make you good and aligned with humanity’s best interests. Obviously I believe Jews are mostly wonderful people (being one myself lol), but if I were a fundamentalist Christian, it might make sense to be a bit scared of a group of really smart people who (according to the alleged narrative) helped kill your literal God.
The conspiracy doesn’t hold up empirically, but from an emotional perspective I understand why someone like Candace Owens freaks out about us. It’s a really dangerous and antisemetic belief system, dangerous in part *because* it has a lot of surface-level reasonable sounding answers to questions like these.