IMO there are two major problems with the bay and mainstream success.
1. Its the home of the independent hustle, artists are less likely to take slave contracts meaning record companies will make less money on them and so not invest as much. Alot of bay artists have been offered or have actually had deals with major record deals.
2. The Bay has no easily identifiable selling point or style that the masses wish to hear. The biggest consistent thing to come out of the bay has actually been conscious rap however everyone and their mum wants to do mob music. The west sprang to fame on controversy, gangs and G-Funk, east coast pure lyrics and beats and later on flashy lifestyle tracks. South used crunk as a platform even though they have many other styles they were trying before they got attention.
The bay had two ways into mainstream i think they should have stuck with, conscious/ghetto life rap and hyphy but blew them both mainly because everyone was thinking short term and being selfish. Admittedly conscious rap has always had a smaller market and according to many bay artists record companies tried to shut it down in favour of sexplotaion and gangsta tracks. That didn't stop some of bay artists having gold and platinum hits or have critical acclaim such as E-40, C-Bo, 4-Tay, Spice One, The Coup, Zion I, Too Short, Askari X, 2Pac, Hieroglphics etc.
The bay has no identity to those who don't already listen to Bay music, almost everyone is mobbing, smoking weed and selling coke, these are things that other areas have already established their dominance in.
Just my 2 cents/rant