The departure of Xabi Alonso was indeed a regret to the club and hiring Erik Ten Hang as the head coach was the mistake then firing him was actually the exact way to correct it and now hiring Kasper Hjulmand is the wise decision to take, I strong believe he will bring back the team to it winning ways, I'm not really expecting a performance like that of Xabi Alonso but hopefully he won't disappoint, he's kind of play tactics and formation will definitely set back Bayern Leverkusen to their normal state, rather than that of Erik Ten Hang, like I really believe he can handle the job well.
Departure of a head coach and star players in a single summer transfer season always cause big troubles for any club and Bayer Leverkusen is not a lucky exception. Their target in Bundesliga this season is quite not too high, as winning Bundesliga title is not their target, while to get a position in top four of Bundesliga, they can do it.
Ten Hag joined and left Bayer Leverkusen in surprising ways but the club has to move onward carefully and calmly if they don't want to finish this season terribly by creating internal chaos.
First of all it was never the intention of Bayer Leverkusen to let Xabi Alonso leave the team after helping them to win the league but when happened was beyond their control so they couldn't stop him, Ancelotti was leaving the Real Madrid team so they contacted Xabi Alonso you don't expect him to reject the biggest team in the world when most players are rushing to play in Madrid. Leverkusen should have waited a little instead of going for Ten Hag but now that he's no longer there
Kasper Hjulmand should try to do better.
Bayer Leverkusen were aware that they are not able to keep Xabi Alonso and star players in their club a long time. Before a short successful era with Xabi Alonso, about 20 years ago, Bayer Leverkusen got success with a generation of Lucio, Ballack, Ze Roberto and they aldready experienced star player departure wave after successful seasons.
With Xabi Alson, Bayer Leverkusen even got bigger achievements than with Ballack generation, as they won Bundesliga title while with Ballack and his teammates, they only finished in a second position in Bundesliga, Champions League and German domestic cup.