Background checks for political appointees are run out of the FBI's administrative rather than criminal division. These investigations are (at least in a normally functioning Justice Department) independent and free of political interference from the White House or Congress. By contrast, background checks like Kavanaugh's are done on behalf of a requesting "client" — in this case, the White House. They are typically limited to interviews with people who know the subject and checks of criminal records and credit history. The subject usually provides references, the FBI interviews them and then asks for other references, building an expanding circle of information.

Source: CNN March 18, 2021 01:18 UTC