What is the Prop 13 trap and how does it affect California CRE buyers?

Prop 13 caps annual assessment increases at 2% per year. On sale, the property resets to full market value. A $5M building held for 20 years at a $1.5M assessed value suddenly generates a property tax bill based on $5M. New buyers frequently underwrite based on the prior owner's tax bill and get blindsided post-close.