It's a strange one though mate. I mean, considering we stayed up by the skin of our teeth you'd think we would be wanting to get players in very early to give them every chance of hitting the ground running.
Maybe, Suso was given the remit of lining up players for both outcomes and those that he came up with for staying up were simply not deemed good enough to push us forward? Hence, they parted ways and brought in Lange. Maybe he has been given the remit of what is required and he's in the throes of delivering such requirements.