Does California subsidise entertainment industries?
Taxes?
Greater pool of talent due to the education sector being more based around entertainment?
Why do we all grow our food in Europe/America when costs of living are so much lower in Asia/Africa? Usually, it's down to subsidisation, tariffs, etc. I'd imagine that the entertainment industry is quite important to the Californian economy - and as such, they'd be willing to offer tax breaks / subsidies to firms within that industry to encourage them to stay.