This is complicated, politically.
If Trump gets sent up the river for the rest of his life, it doesn't really matter what the grounds are. For a variety of reasons, Biden would strongly prefer for Trump to be jailed by the state of New York for tax fraud. Failing that, the next best alternative would be to jail him for fraudulently misrepresenting the value of his businesses (on the discrepancies between his representations to creditors and the IRS/state agencies regarding asset values).
Action by the state of New York leaves Biden's hands clean, and Trump's prosecution as non-partisan as possible. Jailing Trump for fraudulent dealings with the IRS raises the specter of future opposition trying to weaponize the IRS in reply, but it's a lot more politically palatable than jailing him for January 6th. The two of us can agree that Trump incited an insurrection. To Trump's followers, it looks like a politically motivated prosecution, which will in turn make them supportive of pure political prosecutions once the Republicans reclaim the presidency and DOJ.
The other problem with prosecuting for January 6th is proving that Trump was the ringleader, which gets tough due to the degree to which he tends to insulate himself from the criminal activities he orders. Nothing ironclad enough to likely get past a jury has hit the press yet. Garland is the guy that ran the OK City, Unabomber and Atlanta bombing cases for DOJ, and earned a lot of praise for how he ran those cases. He's not going to move without enough to have extremely high confidence of winning at trial, because the absolutely cataclysmic outcome is for the government to try Trump over January 6 and lose.
www.cnn.com
