The only one who can check for maliciously published certs is the entity authorized to request them. I think most companies are happy when they manage to have valid, not expired certs and do not care too much about making sure there are not too many of them.

You are right that if the state would start issuing malicious certs en mass that would be found out quickly. But I think very targeted selected operations against entities where they know the entity is unlikely to surveil for unauthorized certs are very much possible.

I'm not arguing for going into conspiratorial thinking and claiming CAs are all compromised and issuing malicious certs all the time. But I do think that it is feasible for states to use CAs under their direct or indirect control to run targeted attacks. I think that is a plausible, serious risk that we do not care enough about and that we should do something about. There is a multitude of precedence starting from LavaBit over the wiretapping of jabber.ru^1, ANOM^2 to CryptoAG^3 that supports this conclusion.

[1]https://notes.valdikss.org.ru/jabber.ru-mitm/ [2]https://en.wikipedia.org/wiki/Operation_Trojan_Shield [3]https://en.wikipedia.org/wiki/Crypto_AG