I don't believe it's that simple. A lot is lost in translation. Biesla is a success despite it. It's no secret that managers and players regularly struggle with language barriers.
Either way, my point is mainly that there's a lot more to this than just transferring a manager. He's a person at the end of the day. Who know what factors might interfere with a move.
From quickly googling, an interview in January showed exactly that. His own opinion was that his English needed to get better before he could think about coming to England.
These are the things that make or break moves, and mostly we just don't know about them. What seems obvious to us from the outside may just not be the case.