California is a big state, with a lot of people in it, as mentioned by @tinyfaery. Just pure statistics would mean there is a statistical likelihood of there being more business in states with more people. Once an industry begins to take hold in a location, like the tech business, then new tech businesses start to pop up even more, because employees begin to start their own companies, companies locate there because there is a large population of people trained in that industry, and even further on that point universities in the area start to develop and expand their majors in those fields. Since it is a coastal state it is likely to have American headquarters of American companies for Asia as well. For instance Pepsi International Headquarters for Latin America is in FL. Direct TV for Latin America is also Headquartered in FL. Michigan has the auto industry, and a tremendous amount of universities that offer mechanical engineering degrees. Also, Research Triangle in North Carolina, which is the Raleigh-Durham area, is the silicone valley of the south. Texas has Aerospace because of NASA in Houston. Delaware has a lot of banking and creidt card companies because of their tax laws in that state for those businesses. Nashville has the country music industry. New Jersey has a lot of pharmaceutical companies. Fashion Designers tend to be in NYC. There are HQ’s all over the United States.
And, back to California, it is a desireable state to live in, so it helps attract employees. Beach, mountains, the only real negative is it is very expensive in most places. Probably California was more attractive 50 years ago, when many in the northeast were moving to California, before it became so expensive. The next migration to a sunny warm place was southeast FL.