From the start, many people predicted that he would not be able to bring Leverkusen to achieve the success they had when they were coached by Alonso, at most he would only bring Leverkusen to stay at the bottom of the Bundesliga without really being able to compete for the championship title, just like he did to Man United in the past. so Leverkusen's decision to fire him was the right one because there was nothing he could do for the club, at most he would only make things worse for Leverkusen, so rather than regretting it, it would be better for him to be fired sooner.
I do not want to believe that any one taught ten Hag was going to help Leverkusen get anything really good from the Bundesliga this season, the era of xabi is far much better to be ever compared with this, the only best ten Hag would have got them is not allowing them get to the point of relegation otherwise nothing good was actually expected of him and I stand to be one of such person with that taughts.
I think Xavi Hernandez would be a good candidate for Bayer Leverkusen, but I've read somewhere that he rejected their offer. Xavi should have been the main candidate for Bayer Leverkusen before Ten Hag. We know the quality of the Spanish manager. Barcelona recovered from their recession during his tenure, rose to the top, and won the championship. He could do the same for Bayer Leverkusen.