Exactly, even Chelsea finished low 2/3 seasons back but now they are World champions, Nottingham as you said are also good example even when they deserve a spot in the champions league. They did really well and even this coming season I expect them to perform even better but this season will be though for everyone. Any team can improve and I won't be shocked if Manchester United also show some improvements.
Nottingham forest were set to qualify for Champions league but they were not able to perform well towards the end of 2024/25 EPL season. Nottingham forest finished 7th last season and they must be happy that they atleast qualify for UEFA conference league. That's a big achievement for a team that finished just one spot over the relegation zone in 2023/24 season.
United finished 15th last season and as I said if Nottingham forest can make a comeback in next season then any team can do that provided they identify their weaknesses and fix them.