I do not know either. Wilson is also very conservative. He even endorsed Ted Cruz in 2016 and has long been conservative on immigration.
Wilson was right on taxes and crime.
Immigration was an issue more favorable to the GOP in the California of 1990.
California, at the Presidential level, was a swing state in 1990. It had recently recalled its Supreme Court Chief Justice for anti-death penalty rulings. It had a large number of defense industry workers that were Republican-inclined and viewed the Democrats as the party of DoD cutbacks. Its demography was NOT the majority-minority demography it is today.