Better to stay off for a while without having a coaching job than to be in a situation where you are left with what might not give you an impressive result to your CV. That's a more bad record than going off the radar. Moreover, coaches take a leave for a year+ just to have sometime of rest away from the troubles and stress of the job and later return to business.
I am not sure that the Bayer Leverkusen sports directors and management are unaware how the situation might be. Perhaps they just wanted to make some money out of the players they have.
After a terrible season at Manchester United, this should have been the best thing Erik Ten Hag could have done for himself, but since Erik Ten Hag insists Manchester United is the reason why he performed poorly at Manchester United, I believe he agrees to coach Bayern Leverkusen just to prove he isn't responsible for his bad performance at Manchester United. Erik Ten Hag didn't know he was walking into a trap when he signed to become Bayern Leverkusen head coach. Erik Ten Hag is just lucky that the German Bundesliga league is not strong and competitive like the Premier League; he couldn't have made it to the top 10 in the Bundesliga table next season since Bayern Leverkusen sold most of their best players this season.