I went to OpenSecrets.com and it looks like he has contributed to both. I suspect that he is fairly pragmatic but unfortunately the pragmatic thing to do in elite circles is to dump on President Trump.
For whatever reason, the elites seem to have a lot of very questionable sacred cows. Maybe he’s a libertarian?
https://www.opensecrets.org/donor-lookup/results?name=Jeffrey+Bezos
Bezos is a confirmed member of the Political Left.
On the other hand, Amazon's political action committee actually favors GOP candidates.
Bezos avoids most national issues and national candidates.
However, in Washington state, he supports Democrats for every major office, and he supports all the major voter initiatives supported by the state Democratic Party.