The big takeaway here is: Web PKI is fundamentally broken, and the existence of CAs as a concept is the vulnerability that must be fixed -- or, more specifically, the idea that ultimately trusting a relatively small, basically fixed/hard-to-change set of (mostly) commercial entities with something this critical and far-reaching is (or ever was) actually a good idea.

There are a lot of reassuring statements from browser makers and others about how their mitigations for exactly this scenario kicked in and protected (some set of) Internet users, but IMHO there is not nearly enough discussion happening about fixing things so those mitigations are not needed to begin with.