That argument is completely misplaced here. PG&E is a rate regulated utility, which means its profit margin is based on its costs and investments. The rates are set to ensure a modest profit, generally between 5-10%. That means that to the extent PG&E underinvested in safety (lowering costs), it was ratepayers that benefited, because that kept rates low. Investors, by contrast, earned a low return on the stock, and will have their equity largely if not completely wiped out in bankruptcy.

This is a recurring story in rate-regulated utilities all over the country. Public utility commissions want to keep rates low, generally artificially low. So they set rates in a way that causes utilities to externalizations risk or pollution. For example, water rates in the US are very cheap because water utilities routinely dump untreated sewage into rivers. If you forced say DC Water to never dump into the Potomac again, it would have to invest massively in storm water management systems, which would in turn drive up rates.