Actually, it wasn't a "fairly conventional Republican presidency". (At least, not for any value of "conventional" I would recognize.)
Trump launched a major attack on the metastasizing Federal bureaucracy, with his "don't add a new regulation without getting rid of two old ones" campaign. IMO this frightened the lower-level bureaucrats so much that they were all in the tank for "Biden".
Granted, it didn't really affect that many regulations, but it was working (as even the “Deep State” admits), and with another four years there's the risk that it would become so accepted that subsequent administrations would have a public fight on their hands if they try to reverse it.