I get that Microsoft is trying to reinvent itself, but at the core they are (were?) a software development company. It kind of looks bad when you throw your hands up and say “this is just too complicated, we’ll replace it with an OSS component”. Don’t get me wrong, there is no love lost for IE or Edge from me, I’m just baffled at this move.
I think it speaks of a maturity not common to this industry. Pick your battles and battlefields (mutables) after considering resources and the environment (immutables). Conceding Edge will doubtless let them divert focus and resources to areas that are of greater strategic value.