I would have love to see Reuben Amorim struggle to win matches at Manchester United so that you will see what I am talking about, but I won't wish Ruben Amorim that because I want the glory days to return to Manchester United so that they can challenge for the premier League title and champions league trophy. The fact that Bayer Leverkusen management sold their best players to other clubs, they will continue to struggle this season even with a new coach.
Leverkusen have lost three important players as well as one of their best managers and their overall performance is getting worse. Now if they bring a good manager to their club, that manager may not be able to improve the team's performance as before because the club will continue to perform poorly in certain positions until the players who have left do not come to the club. Last season Leverkusen competed to the end but Bayern Munich was ahead by a point margin for a long time that is why Bayern Munich won the league title but the season before that we saw Leverkusen win the league title without losing and it was a great achievement for them. If they want to get that glorious record back then they have to forget about the financial improvement of the club and bring good players to the club then this may be possible.
I do not think it can be as easy as buy stars and everything resets. What has become of United this summer: they spent €250m, 90% of it on forwards, and they cannot play 3-4-3 at all because they lack decent wing-backs and a midfield controller. It is the same structural hole as Leverkusen but the opposite way round: United had overspent without fixing the keystones, Leverkusen had sold all of them at a net profit. The two styles killed performance. This is why I do not believe in the manager will fix it. Alonso had Xhaka with 79% press resistance compared to the guys in the 60s. You remove that and then the entire set up falls apart. Even when you have Klopp, the statistics tell you that you will concede at 2.5 goals per game until you re-establish that midfield shield. Personally, I consider this to be a two/three window re-construction.