Trump is damaged goods.
They'll have to figure out new ways to attack DeSantis (or any other Republican candidate) and find out what sticks.
That takes time.
They weren't able to do that to Reagan. They were eventually able to do that to Dubya but it took them five or six years before he was tarnished in front of the American public.
Trump is the opposite of damaged goods. When they strike him down he rises up more powerful than the left ever imagined.