This is why we shouldn't underestimate Ten Hag. Leverkusen wouldn't expect too much from Ten Hag because they have known his past and hiring him means that they're ready to work with him. On the other hand, Ten Hag will also want to put in the best of his coaching skills into the job, so that Leverkusen wouldn't be disappointed in him.
We saw that Ten Hag was not successful with Manchester united , no one can rely on Ten Hag. And that is normal. At the same time , leverkusen does not have a strong squad that will compete strongly for the Bundesliga title. And I think Leverkusen management knows this very well.
We also see that Leverkusen has sold several important players in its squad. If Leverkusen management had a full intention to fight for the title, they would have tried to strengthen the squadl, not sold important players. That is why I would say that no one expects Ten Hag to fight for the title next season. As long as leverkusen's performance is stable, the leverkusen's fans will be happy.