You are assuming his reason was valid, but you refuse to come up with a single legitimate reason he could have used.
I think people will keep asking. I'm sure his team is furiously trying to come up with one other than, "I wanted to leak it to the press" or "I wanted to enable Dem operatives in the Justice Department to work against a duly elected president." Honestly, I didn't think Biden was smart enough for any of this stuff, so I assume one of his underlings or another Dem operator had him do it as the fall guy.