Sticky to dismiss that position without cause. The IGs appointed by the President require 30 days notice to Congress with the reasons for the removal. Would agree he’s more than earned it, but Papa Joe’s not going to do something without thoroughly dotting the t’s and crossing the i’s.
In general, you might be surprised how many appointed positions get held over for years between administrations.
Hell, the Ukraine Ambassador that almost took trump down three years into his administration was herself an Obama appointee.
With over 4,000 appointed slots to fill, a Senate that works 2 weeks a year, not a lot of time to fill all the gaps out there.