Ok, let's talk about how the signings performed under the manager they were signed -
LVG - Shaw, Shmidfield, Di Maria, Rojo, Depay, Darmian were all flops under LVG. Jury was out on Martial. Herrera had been ok and Blind was good
Mou- Matic, Lindelof, Fred, Mkhi Sanchez were all flops under Mou. Pog was more on the flop side. Jury was out on Dalot, Lukaku (barely) and Zlatan can be called success under Mou.
Ole - Maguire, AWB, Bruno, Cavani can be called success. (You may not like the 2 defenders, but they've done well here). Jury is out on VDB, Telles. James would be called a flop so far, and Ighalo was meh(but did what he was brought in for).
Ole is quite comfortably better most managers when it comes to transfers and squad building, and I'm not sure I'm having to have a debate around this