Another one I could see is that he wanted to vote Republican but at some point realized that Trump sucks ass to put it mildly. So he tried to somehow push the Rep party to at least get back in touch with the idea of sanity by killing him?

I could see that happening. While I still dislike it, conservatism by itself is a valid ideology. Maybe he believed in the core principles of the party (small government, free market, christianity, etc.) and was sick of the main candidate being a lying fascist that is the spitting image of the biblical antichrist.