I thought about giving examples because I understand why people would ask for them, but I decided very deliberately not to give any. It would inevitably turn into a flame war about the politics/ethics of the specific examples and distract from the reasons why I no longer trust Wikipedia.

I understand that this is unsatisfactory, but the only way to "prove" that the motivations of the people contributing to Wikipedia have shifted would be to run a systematic study for which I have neither the time nor the skills nor indeed the motivation.

Perhaps I should say that am a politically centrist person whose main interests are outside of politics.

Let me guess: you hold some crank views that aren't shared by the people who maintain Wikipedia, and you find that upsetting? That's not a conspiracy, it's just people not agreeing with you.