I don't think it is the Microsoft part or that anything becomes evil merely by changing hands. Just that the network effect of chat clients or social media platforms in general is so finicky that changing hands might be enough to cause some splintering of people off to the next thing.

I feel like it is getting longer and longer between the next biggest social media, but there has been a lot of chat clients over the past 2 decades. I don't think many people have any company loyalty in this market. The main thing people care about is that the people they want to chat with are already there. If people start moving to something new for whatever reason then everyone else will likely follow.