They left because they screwed everybody they could and had nobody left to exploit.
Once they make their money and retire with those generous public pensions they head for greener pastures in Oregon, Nevada, Arizona, Idaho -- and then turn those states into mini-Californias.
They pretty much succeeded in Californicating Oregon and Washington. They are half way there in Colorado. AZ and Idaho are still Red though.
Most of these liberals are recent arrivals to California (a couple of generations). They came from New England and the rust belt.
Now that they have ruined California they are moving to the southwest and the northwest.
Rather than stay and fight these carpetbaggers many conservative people choose to take their families elsewhere.
Isn't that exactly what the Iraqi people are doing? Fleeing the battle?
It may be a little late for this state. But the lesson to be learned is: stay invested in local politics, fight every encroachment of socialism/Marxism.