Would it be desirable for a state actor to have a foot in an email provider or VPN service? Sure (as it would be having it in other areas too - like iOS and Android, macOS, Windows, password managers, hardware, cryptocurrencies just to name a few).
Could it be that “something big” is going on in the background without the world knowing about it? Absolutely possible - the Snowden leaks have shown it.
If you use your human intuition to question whether Proton is trustworthy or not, that's absolutely fine.
Nevertheless, I think that asking the question the way you're asking it will ultimately lead to nothing useful except that you'll end up with a series of assumptions, feelings, fears and opinions on the subject and end up just as wise as before.
Maybe it would be a better approach to ask whether anyone has some kind of evidence for your assumptions.
If there is no such, I would at least look at clues (in a sense of "circumstantial evidence" - I'm not shure if i'm translating it correctly) that could confirm or invalidate your intuition. Helpful steps off the top of my head (please feel free to add) could include the following questions:
Can you (or a talented developer you trust) look at the softwares's source code?
Are there independent security audits?
Does the company have a viable business model or is there a lot of volunteer work keeping the project alive?
Taking this approach, for me personally this brings up other email/VPN providers than Proton that would raise more red flags for me.