From the look of things he's great at communicating with players. And know exactly what Man U needs to lift up their position in the premier league. Especially this season that the competition is high and tough. Any team that doesn't offer their best would be left behind not minding how big they've been in the past. The story behind Man U backward results stems from the management. And a good manager is the one loved by both the fans and players, a team player that could bring out the best in his boys. And that's who Ruud is. The fans love, gives him the charisma to deliver, and not to lose the respect of the club.
Fans love their ex-legendary players like Ruud van Nistelrooy to become their head coach, and give the coach huge support, but it does not last too long if the coach can not lead the team to success or at least good results. The relationship between a club coach and fans can be broken very quickly, as well as between the coach and club owner. Ruud has very short time as a temporary head coach and it's sweet time for all, hopefully he will return to the club in future with a head coach position.
However, Amorim on the other hand, won't be a failure, he's making new decisions and would add players who understands his pattern of football to the first 11. He's the type that'll revive some of the benched footballers in the team, and feature them more in matches. Which isn't a wrong move.
Amorim did great jobs in Sporting Lisbon and he has very bright future but between Sporting Lisbon and Manchester United, there are big differences from pressure, expectation and challenge from stronger competitors in the league too. Amorim has some necessary things to succeed in Manchester United but he has to learn many things in a new club and new league too, it's generally very challenging.