One is that a lot of people in Calif don't want to buy electricity from Diablo Canyon.
PG&E offered a very different reason for closing Diablo Canyon when it set the wheels in motion in 2016.
According to legal documents PG&E submitted to the California Public Utilities Commission, the utility anticipated lower demand not for energy in general, but for nuclear energy specifically.
One reason is a growing number of California residents buying power through local energy purchasing groups called community choice aggregators, the 2016 legal documents say. Many of those organizations simply refuse to buy nuclear.
There are 23 local CCAs in California serving more than 11 million customers. In 2010, less than 1% of Californias population had access to a CCA, according to a UCLA analysis published in October. Thats up to more than 30%, the report said.
https://www.cnbc.com/2021/10/02/why-is-california-closing-diablo-canyon-nuclear-plant.html
The other point I will make is that the solar totals for Calif is probably under counted. Google says that there are 230k homes in Calif with solar panels. In my system the local utility knows how much I send back to the grid, but I don't think they know how much I used. They can probably estimate it though. In order to be grid-tied I had to register with the local utility so they know the size of my system. It wouldn't surprise me if there is a group at PG&E that is telling them how much revenue they are losing on a sunny day...