The thing is that Football doesn't work like that. We don't know who the next manager is going to be.
DS was given time to build an identity that culminated with us leaking goals left right and centre (13 in our last 4? or something similar), with no discernible pattern of play, and lumping on 4 strikers in his last match in charge. I can't see how more time would have made a difference. I understand injuries and bedding in new players etc etc, but that's all part of the managers remit, and it didn't work out. That's football.
DS always has long winless runs, i think that is fairly undeniable from Walsall to Brentford to us. The PL has 38 games a season, the Championship has 46. Long winless runs translate badly in the PL, as you have less room for manoeuvre, and a long run of bad results ends up with CEO's and owners getting very nervous as you sink down the table.
It's a shame it didn't work, because the vast majority of us wanted him to succeed, but it didn't.