Because Obama admin made the choice explicitly not to charge Assange because of the risk to press freedoms. You even had the general counsel from New York Times arguing this for the last several years. If you charge Assange with these "crimes," you're opening the door for other publishers of the same information to be charged. New York Times, Washington Post, everybody.

Trump admin was the one who changed their minds and decided to nail Assange to the wall with the hacking claim. (Big surprise, loyalty is a one way street with Trump.)

Look, Obama legalized and formalized the worst excesses of the Bush administration, but this is one thing he did right. If we're gonna say Biden is gonna follow Obama's lead, that means the charges will be dropped.