Could it be because adoption was already high and ground space is more limited in SF county than any other county in California?
I think partially but you missed a key factor which is that most new homes in California require rooftop solar. So the net-metering change only affects individuals adding solar since it’s optional for them. SF builds an extremely low number of new homes compared to the rest of the state, so they have less of a foundation to fall back on when individuals stopped installing systems.
No
"The sudden drop in solar panel applications is in large part due to the enactment of a new rate structure for paying solar customers"
Does it mean that production reached the level where intermittence becomes problematic?
No, it mentions what is happening in the article. California did some shenanigans that made solar less appealing. Less earning from pushing back excess energy to the grid, etc. There is less incentive to have install solar.
everything about energy production