I completely agree that those are without a doubt the main drivers. 
But it's still curious why the outcry for no-kyc and verifiable security is so big, and there's still a good amount of software used that doesn't follow those principles as much as they could.

To be fair, there is a telegram FOSS https://f-droid.org/en/packages/org.telegram.messenger/

bitcoin

Why are most Bitcoin groups on Telegram (and not signal, wire, etc.)?

Probably for the same reason Bitcoiners are on Twitter and not Mastodon - network effects and features. We have strong incentives to be principled when it comes to money - because the alternatives are failing categorically. The need to be concerned about the fate of communication platforms is mostly hypothetical today. If the alternatives to Telegram want to win, they'll have to provide incentives by being 10x better along some product dimension that users actually care about - FOSS and privacy aren't big concerns for enough people.