No matter how much amount of money was thrown at him, Zlatan would never sign with United if van Gaal was still the manager. Slate him all you want, but Mourinho certainly has his pulls. Plus, he has already delivered two trophies, and his teams are always better in the second season. We're trending upwards as a club under him, which is something no one could claim after LvG/Moyes seasons.
He delivered a League Cup and a Europa Leauge. United should have won the Europa League from day one. On top of that the club spent a fortune bolstering the side for him. IMO Mourinho has made somewhat of an impact, but you're giving him too much credit.