Ten Hag should be given support, he was a good coach before but what happened when he was at Manchester United destroyed everything, I think overall and it's not just Ten Hag who failed at Man United but several previous coaches did too so I still think that Ten Hag has good qualities like he did at Ajax so there is also a possibility that he can rise better with Leverkusen but the lack of management support makes it a bit difficult.
Just before you compare Ten Hag's performance at Ajax with that at Manchester United, take note to know that both teams are in completely different leagues with different challenges and different competitive challenges so he may not be able to replicate a performance from the former to the later. As a coach he is deserving of every form of support which is a very good and agreeable point, from the team, fans and the management of the team he headed as a coach, he got some good support until a time when they were no longer getting good returns from their support. At that time Ten Hag's system was failing and the results weren't coming and so he got all the reactions that came to him and this does not make him a bad coach, he can achieve better at Leverkusen if he changes some of his strategies to suit the league where he is now managing a team.