That is true, if Pep or Ancelotti manages either Manchester United or Chelsea, there's no doubt that the club will enter into the top 4. But we still know that both Pep and Guardiola cannot be your coach and you as management fail to supply him the quality players that he needs. They will not even agree to the contract if you don't state how much you are willing to give them to buy players. Those guys are big names and they do big deals. They don't manage or beg the club to keep them because they got some proven record of excellence. This is just the real state of matters.
Absolutely right, these guys will never agree to work with the club if it cannot fulfill all their demands. This is the high league of coaches who value their reputation very much and they simply will not allow themselves to start coaching a team in such a state as Chelsea or Manchester United, or the management will have to almost completely update the squard, which implies huge expenses on transfers, which few will agree to. Money can decide a lot, but there will always be other criteria without which it will be impossible to become a champion.