I know most folks have read about mob mentality even if they've never experienced it. Perhaps a pack of dogs or wolves can be more readily understood. Hurting or subduing and individual does nothing to slow or break up a pack.
Like a pack, mobs can only be stopped by stopping all members OR, sometimes they can be stopped by shock. If the police selected a person or two from the mob and disemboweled them before decapitating them and mounting their heads on pikes while simultaneously projecting their actions on skyscrapers and all media channels with amplified sound of every drop of blood hitting the street, they might be able to defuse the mob.
Since no one is willing to pay that price, police do their best to ride it out.