There are people leaving California, and California's population is huge. But the rate at which they are leaving is less than that of many other states, and the main migration is within the state. You are seeing a lot of Californians because there are a lot of Californians.

This isn't new: a couple of decades ago you saw a ton of people from California buying up property in the Portland area back when California's population was booming and Portland real estate was cheap.