It's because the California government doesn't believe in markets, prices as incentives or anything like that. California govt believes in state mandates
You understand there are multiple types of regulation, right? The deregulation you're referring to was with respect to generators being able to sell into the grid.
The relevant regulation here is the state-backed guarantees on returns for pge under authority of CPUC. CPUC approves basically any rate increases pge approves. It doesn't need to do this. It could hold pge accountable based on what they determine qualifies as operating expenses vs. infrastructure improvements. PGE wants everything to count as infrastructure improvement because they're guaranteed a rate of return on infrastructure projects.
Obviously it's difficult to determine what "infrastructure improvements" were actually due to poor management and maintenance vs. what infrastructure improvements are required purely to meet demand (for example) or from "normal wear and tear".
It's hard to reconcile 1) the fact that there's pretty broad consensus that PGE fucked up and didn't fulfill its obligations, especially maintenance and 2) reporting record profits. Clearly there's something wrong with the system, particularly the CPUC-utility relationship. AKA, regulation.
I understand that. I'm simply stating that GGP's assertion that California "doesn't believe in markets" is at odds with the reality that Pete Wilson signed a law that made California the very first state with an electricity market.