I see that as offering services that people clearly use and value, and that the bills have to be paid somehow. So as long as proton can deliver the privacy and security features it promises, I personally don’t see anything wrong with providing an alternative when the only other options are built on monetizing your data.
Flip flopping implies indecision regardless of validity of fact and switching without good reason. If there is good reason to switch, then it is simply making an informed decision. People who don’t change their stance when presented with convincing evidence to the contrary are cultists.