California's tax regime is really backward. I suspect Tesla's departure is just the tip of the iceberg and that the repeal of the SALT deduction in 2017 really hastened this trend.
High earners pay an effective tax rate of > 50%. They are partially picking up the slack from Prop 13, which artificially distorts the housing market by allowing longtime homeowners to pay property taxes based on decades-old assessed values while sitting on millions in equity gains.
So young, high earners see the state taking a massive chunk of their paycheck in exchange for middling infrastructure and pitiful public schools while simultaneously putting its finger on the scale of a wildly inflated housing market.
The exodus will only pick up steam unless policymakers get their act together.