Man U only started showing good results at the end of the season... But failed to achieve anything other than a place in the Champions League next season... It's probably too early to talk about any success because Man U has always been a top club that has often played in European Cups... This season they haven't won a single trophy, although they have competed in many competitions... I think they have a lot of work to do...
I would say given the pit they were in last season, it's tremendous achievement for them to make into top 4 at least. They have gone through a lot over the years so they did well. Also you can't expect them to get hands on everything in just a season of rebuilding. It would take a bit more time before they really can be considered as a contender in competitions. This season they actually won EFL when they faced Newcastle in the finals and scored 2 goals.
I would however agree that they still need to work a lot and hopefully ten Haag will cover that in next season.
I can't say that last season the Red Devils had a much worse result than this season... They got a place in the Europa League and didn't do too badly, but they lost to the reigning champions, Sevilla... Chelsea have had a really bad result this season, and if they qualify for the Champions League next season, it can probably be called a good result... Man U, on the other hand, are playing at an average level...
Manchester United were a very weak team at the start of the season. But they have managed to correct their mistakes. And at the end of the season, they are third in the table. It was a very good season for Manchester United. However, Chelsea have played very poorly this season. After the change of coach, their performance has become weaker. Chelsea is the 12th team in the points table. There is no guarantee that they will be able to play well in the next season. Chelsea will definitely need to spend a lot of money next season to build a stronger squad. If not, Chelsea's performance is likely to remain erratic next season.