Re: It's not just IR35 though
Cromwell was just the top guy of the religious-military junta.
Charles Second was more a case of deciding to go back to the old ways was the least worse option after the Republic/Protectorate. At least insofar as England was concerned, Scotland and Ireland suffered in their own different ways. And the swing of power to Parliament meant it was a different type of monarchy afterwards - and thus get to replacement of James a few years down the line.