I completely and utterly think it's MS abusing their monopoly position (again). Slack, Zoom, etc, all cost actual hard money.
Microsoft released Teams for effectively for free, paid for by existing (extortionate) subscriptions (that are never in the public domain). Now, despite the product being almost _universally_ hated by its users, it's number one.
I think so, yes.
I could also imagine that business people:
1. see effort in integrating Slack/Matrix/..
. into their landscape
2. think MS is a big name and thus will build a proper product
3. see no big difference in terms of functionality.