That's just independents.
Overall, DeSantis is just up +0.2
And he hasn't declared yet. You're going to have over a year of Trump and his fans going at him, plus other candidates, then the Dems. They're going to drop it on him.
Then, if DeSantis gets the nod, those hardcore Trumpers are going to stay home, enough to make a difference. Just like those hardcore Sanders supporters stayed home, enough for Hillary to lose. Trump will say the RNC cheated him, they're corrupt, usual routine. No way he falls in line behind DeSantis, he might run independent if he loses the Republican nod. He's a burn it down type. Those hard core Trumpers are cult like. Never will they support DeSantis. They believe all the lies Trump will tell them.
Biden wins no matter if it's DeSantis or Trump.