To support my explanation, see for example this:
https://www.theverge.com/2020/10/25/21532883/paypal-cuts-tie...
PayPal terminated Epik's account, because they refused to kick out Gab. I believe there were a couple more cases where the money people pressured companies to do things like that. My memory is getting blurry with this though, so I can't point you to the articles.
And that leads me to something even more important. Gab was not only kicked out off their domain registrar, but the owner's family was blacklisted by Visa. So the social media is actually the least of my concerns right now, the most urgent thing at the moment is regulating the banks, so they can't terminate your account for no reason. Because they will come after your money at some point. And good luck paying in cash in a middle of pandemic.
There's a much simpler explanation: Google wants as much of your communication as possible to go through them or their partners, so they can monetise it. People using Parler or Matrix don't leak any information to Big Tech, so commercially it makes sense to deter people from using apps like that, and they'll use whatever excuse they can get away with.