I know nothing about nothing, but I always assumed that all the money was from Hollywood and Silicon Valley. Outside of those two highly localized industries, is there really much more money than other states have?
It has it's own wikipedia page: https://en.wikipedia.org/wiki/Economy_of_California
Its agriculture industry is about 50% larger than that of the #2 agricultural state. It also has the largest manufacturing industry. It is #3 in defense (about 20% behind Texas and 12% behind Virginia, and almost twice as big as #4 which is Florida). It is #2 in financial services behind New York.
California also has ports and railways, servicing the vast majority of trade with China. It has the strongest agricultural industry in the union. Aerospace industry from manufacturing to space launches. Worth mentioning the the oil and gas industry. It will take a long time for all these to be gone. It's easy to move Twitter or Tesla HQ to another state, but physical production is not as mobile, the same Tesla's factory is still in California.