Actually U.S. cities formerly were financially responsible for property damage occurring riots. Due to this police and politicians prior the 1970s did their best to stamp down on riots and avoid the financial consequences. Since the 1960s/70s they are no longer financially responsible for property damages which occur during riots (or "civil unrest"). Hence the politicians and police don't really give a damn about stopping riots today by applying firm measures.
Are you implying law enforcement did a better job of “stopping riots” and destruction prior the current methods?
https://www.cnbc.com/2011/02/01/Americas-Most-Destructive-Riots-of-All-Time.html