He's right. DeSantis will get 300 Electoral Votes on Biden. He's 45 years old and Biden is 80. Biden's age would be a much bigger issue against DeSantis than Trump. Independents soured on Trump, but would pick DeSantis over Biden because a)Biden's old, b)DeSantis is young and America likes youth, c)They are stupid enough to believe DeSantis isn't dangerous.
I don't think the Manhattan DA did this for the national Democrat party, but I do think he's using this to make a name for himself and potentially run for NY Attorney General down the line. Or maybe he's hoping to be selected as US Attorney for one of the NYC Federal Districts. He did kind of campaign on holding Trump accountable before he was elected DA. A little too political for my tastes. MAGA has ran with that narrative and said he campaigned on getting Trump before he was elected therefore he came into the investigation with a bias.