Also on front HN page is https://kaba.cx/posts/20261020_Tor/ on how 300 tor exit nodes were compromised.

In that case it was ssh sessions being intercepted.

But my question is if a tor exit node or a vpn provider or your internet provider has a private key to any CA then can they mitm any normal web traffic even though it will show up as https without warnings in your browser?

Yes.