Alright, but why would Ten Hag agree to take a job to a club he wouldn't be getting the funds to sign some of the fine players into his team but rather the club management be selling off the good players he could use for the season to build a strong competitive team. If Ten Hag has to lead another bad season with Leverkusen after leaving United with a bad record it will be a dent to his profile in getting a bigger job after Leverkusen's, it is something he should know.
Sometimes staying very long without a job at hand might ruin some coaches reputation, I think that’s the case if Ten Hag, he doesn’t wants to stay long without him managing a big team, and Leverkusen is indeed a big team that has done well in the Bundesliga in the past two season under Xavi Alonso; therefore, since Alonso can be able to build the team from scratch, he should also do that, it’s all a matter of time.
Letting all the key players leave the club is not proper; the Leverkusen management and sporting directors didn’t make the right decision, they were expecting to get new players that can replace these players as quick as possible not knowing that even if they get players in their respective position, it will take them time to adapt to the team, and it will affect the team for a while.
However, I still trust Ten Hag, he might come up with something surprising, even though I don’t expect much from him due to the players left for him in his squad.
That has never hurt any coaches' reputation. Staying away from football and being selective about the offers they get is actually a strength and can improve their reputation. Everyone here knows these coaches going from one club to the next, regardless of the level of that club as long as they pay the salary. Go from Spain to England to Turkey to Saudi Arabia to the MLS, back to wherever. Those coaches claim they benefit from their extensive experience, but you could see that whatever way you want.
I prefer a coach who is able to stay away from being a coach and take some time and think thoroughly about a potential new team. Back in the days when Klopp left Dortmund for Liverpool, that was well thought through. It wasn't just because Liverpool is free and pays more. He wanted to build something. Most coaches these days don't care about the next country they will live in or the new team they will coach.