TLS was expensive. And insanely profitable. The sale of Thwate to Verisign was north of 600 million. (Back when 600 million was "a lot"). Since the marginal cost of making a cert is zero it was a literal cash machine.
LE broke that cash flow. CAs tried to claim their certificates were "safer" or the EV certs had any value at all. All nonsense, but for a while some layer of IT folk bought into that. Even today some of my clients believe that paid-for-certs are somehow different to free-certs. But that gravy train is rapidly ending.
So yeah, once the fixed costs overwhelm the income expect to see more shutdowns. And naturally the small CAs will die first.
I can't say I'll mourn any of them.