Ten Hag bought less valued players very expensively in United which has put them to the financial situation that they are facing now. Therefore, I don't think that Ten Hag is a manager that can manage little amount of money to buy players. He doesn't even have good taste for quality players because he is an average coach. I feel that Leverkusen is bigger than him and will fail again. Leverkusen needs a coach that will strengthen the team in order for them to win the title and not the opposite.
A coach who gave Ajax two domestic trophies is not an average coach. Sometimes, good coaches face some challenges in new clubs and fail to perform. Manchester United has some challenges that the fans wanted the Glazers to leave the club. Let me say that Erik ten Hag was unfortunate but has Ruben Amorim solved the problem of the club. You will be amazed that the Dutch coach will become successful in Bayer Leverkusen.
I understand your point mate, Ajax is not as big as Manchester United which might the reason why he could succeed in Ajax and couldn't in United. Some coaches cannot face the pressure when coaching a big club because they will be worried and confused due to critics from the fans. Those coach are known as average coaches. A professional coach will succeed in a big club despite whatever challenges that they are passing through. Look at Xabi Alonso who brought Leverkusen out from the darkness.