We cannot pass verdict on Ten Hag's new job just yet just because he failed at Manchester United, let me take our minds back that he was successful with Ajax back in the years before United. This is a new team, a different league and different set of players so expect anything even success. There is also the argument that the so called bad players have become good in their new clubs since they left Manchester United so it’s possible that Ten Hag could be effective at Leverkesun.
It's true, I think it would be excessive to judge Ten Hag without first seeing his performance. With Leverkusen, perhaps Ten Hag will be able to meet expectations. His failure with Man United cannot be used as a complete benchmark, in many situations, everything looks very different. Ten Hag has a good understanding of the Bundesliga, and that will help make his job a bit easier when adapting.
On the other hand, Kompany was also underestimated when he first arrived at Bayern Munchen, so it's actually not surprising to see Ten Hag in the same situation. Every manager has their own strengths and weaknesses, and I think Ten Hag must have learned a lot from his past experiences. I hope he has changed many things about his strategy and approach with players, as that will determine Leverkusen chances of achieving much success in the future.