They don't have a choice. Chelsea were paying Villas Boas and Di Matteo for a few months. In fact Chelsea are usually paying at least two managers given how often they're sacked. It's only until Kenny agrees to a settlement, which he seems to be (rightfully) digging his heels in on.
I'm not 100% sure Croly would be able to be described as "manager" though. He might have to be a Director of Football or a General Managar or something until Kenny is gone.