They have never been politically neutral when it comes to antitrust and privacy (well, antitrust has direct implication for privacy). They spell that out as the exception quite clearly, an thankfully they are not. In this context, praising Trump and/or criticizing democrats in this context is A-okay for me. I did not have a problem even with that being their official position, TBH, but I can agree that it was a poor decision.

They did similar posts in the past, see https://proton.me/blog/trump-controls-nsa-fbi or even similarly political content like this. Additionally, most of the orgs they donate to are clearly politically aligned.

So I genuinely don't see the problem in them having a clear position on antitrust, even if it happens to praise trump or republicans.