With the current conditions, I don't think we should be able to distinguish between the past and the present.
A few seasons ago this strategy might still end with good results as we know where there are a series of great coaches who have been at Chelsea but now it is difficult to happen again.
The reason is because currently Chelsea do not have staff who can be considered reliable like Cech for technical advisors and team performance or the loss of Bruce Buck and Marina Granovskaia from the ranks of Chelsea officials.
Even though they are behind the scenes but in this case we must realize that their role is really very good for Chelsea so that the strategy of changing either coaches or players can still be done because their planning is mature but now they make changes and reshuffles based on desperation for something instant not mature planning.
this is a normal condition that Chelsea is currently experiencing and perhaps will also be experienced by several other teams when every season the players and coaches always change which causes a much different performance update and as we can see, it is not only Chelsea, but Man United is one of them. In all of these conditions, the main key is actually in the management that manages the finances. I mean if management can really manage the finances to buy players and contract the right coach for the team, I am sure a team will never experience a very drastic decline in performance like what Chelsea experienced at the time and also Man United which is experiencing a decline in performance.
this will be a challenge that must be solved by the coach of each team to find ways to improve the performance of their players to strengthen the team in the future.