I actually think that what they have done is bound to fail. The fact that they have actually went out of their way to force/black-mail their new managerial appointment is a great sign of a club that is deeply troubled, driven by short-term + immediate concerns, and devoid of stability/vision. Which is what everyone anyways knows very well about United.
But if bringing Amorin has indeed been part of the Man City plan then they might succeed at very significantly disrupting their closest rival. Stealing their closest rival's ideas, along with disrupting their closest rival, might be their focus especially given the great, great Man City recent success. That could potentially be a concern. But, again, that is just a possibility and a conjecture based on the thus-far easily available information. I don't know if that is actually the case. And I don't really know almost anything about Man City - United relations to know how big of a possibility/likelihood something like that is or could be.