I really have no idea where the idea of sticking with a crap manager for years and winning things comes from. Who has ever done that. Top managers don't take years to build a good side unless they are doing it on a tight budget. We could have given Moyes 10 years and I don't reckon he would have won the league.
Maybe because systems and particular players that managers like can take years to form. Fergie took 6 years to win his 1st PL title.
All comes down to money like you say, if you got loads of it, you pretty much can go out buy whoever you want.