It wasn't done a long time ago because running a CA costs money (which is why they charge for certificates), so whoever signs up to run one is signing up for a money sink with no prospect of direct ROI, potentially for a loooooong time. This new CA is to be run by a non-profit that uses corporate sponsorship rather than being supported by the market; whether that's actually a better model in the long run is I suppose an open question. But lots of other bits of internet infrastructure are funded this way, so perhaps it's no big deal.
There aren't a whole lot of privacy concerns with CA's as long as you use OCSP stapling, so users browsers aren't hitting up the CA each time they visit a website (Chrome never does this but other browsers can do).
Re: CA compromise. One reason running a CA costs money is that the root store policies imposed by the CA/Browser Forum require (I think!) the usage of a hardware security module which holds the signing keys. This means a compromised CA could issue a bunch of certs for as long as the compromise is active, but in theory it should be hard or impossible to steal the key. Once the hackers are booted out of the CA's network, it goes back to being secure. Of course quite some damage can be done during this time, and that's what things like Certificate Transparency are meant to mediate - they let everyone see what CAs are doing.