I don't know why people are doubting Ten Hag and thinking he cannot do much in the club, he is not a bad coach and can definitely manage a team like Leverkusen easily because there is no pressure of any kind in the team like it was was at Manchester United. Manchester United made the job more difficult and complicated for the coaches because they are desperate to become better and didn't want to give coaches enough time to figure things out.
This is a very good opportunity for Ten Hag to redeem himself and I am sure he would also not want to blow it. The German League is not so hard as the premier league and Leverkusen is a well established team already and so they will have access to few good players to make the job easy for him.
If he succeeds then he is definitely not a coach for the big teams.
His display and performance for Manchester United made it so and I wouldn't really blame fans who now kind of doubts him and his pattern. Talking about him not going to be pressured the way he was at Manchester United, yes it might not be exactly the same because both teams are of different levels but in Bayern Leverkusen right now, the previous coach being Xabi Alonso has really set the bar high for any coach that's taking over. The Leverkusen fans now expect a particular style of play and good results from their games. The two years he spent there really made it possible and he even won them the league and domestic Cup.