How? The same as you would if the farmer providing retail-ready carrots didn't exist.
In California's case the grid generation capacity was made up of nuclear (fixed base load), natural gas for dynamic load, and solar/other renewables (wind, hydro etc), and import/export.
If you look at the grid operator stats on https://www.caiso.com/TodaysOutlook/Pages/supply.html#sectio... - I find it interesting to compare days like May 10th (where solar + base load lead to exporting) vs something like Sept 1st (where solar + gas + imports was barely enough) vs today (Dec 16th, where sun is limited and we rely on natural gas + imports to fill the gap).
PG&E probably loses money on days like May 1st where a large portion of their power is acquired at retail, but makes a killing on the other two example days by selling wholesale generated/imported power at our jacked up rates.
IMHO They want to make a killing on the plentiful springtime solar surplus too. Now that they've got everything they asked for don't expect that this will reduce rates for non-solar customers - it'll go to investors.
I still think a tune-up of NEM2.0 would have been better. Other places seem to get by just fine with an 80%-90% buy-back rate vs NEM2.0's 100%.