IMO the key factor is that so many investors are in California and investors prefer to have a founding team locally accessible. What else? Talent? Yes, but at

IMO the key factor is that so many investors are in California and investors prefer to have a founding team locally accessible. What else? Talent? Yes, but at a cost that is becoming unbearable for early-stage startups. Customers? Maybe if you are B2B technology, but most startups are not.