Hake followed sacked manager Erik ten Hag last month.
"Erik’s dismissal and my departure from Manchester have been crazy. Over those four months at United I can fill four VI Christmas specials. The fact is that we have not won enough. It’s just very sad," Hake told Voetbal International.
"I also honestly think that if we had been given more time, we would have succeeded. Becoming champion has never been the goal, reaching the Champions League is. It is often said and written that Erik spent that money and that he brought in all those players.
"But that doesn’t make sense. Manchester United has a scouting force of 40 people or so. Erik did not deal with transfers on his own and you now also see that Martínez, De Ligt, Onana and Mazraoui are just regular players.
"They are just good football players, that has nothing to do with an Ajax past.”