You sure about that? Biden's made it really clear he wouldn't pardon Trump at least, I'm not sure where you are getting the idea that he wouldn't prosecute him either.
https://thehill.com/homenews/campaig...cted-president
Biden told Radio Iowa that he wouldn't follow the example of former President Ford, who pardoned his predecessor, President Nixon, so Nixon would not be prosecuted for his role in the Watergate scandal.
“It wouldn’t unite the country,” Biden said. “You’d say: ‘Wait a minute. I get a parking ticket and I’ve got to pay it. This happens to me and I’ve got to go to jail. This guy does all these things that put us jeopardy and he gets off? I think this is of a different nature."
"I think President Ford, God love him he’s a good guy, I knew him pretty well, I think if he had to do it over again he wouldn’t have done it ... because he didn’t get reelected,” he added.