The problem is that one person's "radical" is another person's mainstream normal. Besides, the FBIs mission doesn't include immigration and naturalization, ie: illegal (terrestrial, as opposed to space) aliens, that's another agencies job. Jurisdictional distinctions aside, these agencies run day in and day out with a minimal amount of political interference, regardless of the party in power. Just like Mr. Trump couldn't stop the FBI/DOJ from looking at his finances for illegal money laundering and foreign influence, Mr. Biden can't snap his fingers and get whatever he wants, either. Yes, political appointees set policy that moves an agency a few degrees in one direction or another, and sets different priorities, but cases take years to unfold, and nobody drops a current investigation to go do something else.