There isn't enough space for urban development in the Lopoc/Santa Maria area. It's really difficult to build on hills and mountains.

As you say, the difference in infrastructure. Long Beach is where the two railroads from the East met the Port. Nearby there was flat, easy-to-develop land with little agricultural value, a good water supply, and oil deposits. Industries like aviation also tended to be agglomerative. The first couple of aircraft builders may have located around places with good flying weather and airports, but the next ones were established by employees leaving the pioneer firms, who tended to set up shop nearby where they could access the same suppliers, financiers, and skilled labor pool.