Ten Hag is as much the opposite of Alonso as he could be, there are literally zero similarities between the two coaches. I think it is a mistake, but who knows maybe it is owed to the fact that not too many coaches are available at all.
Erik ten Hag is a pretty good manager. Take a good look at his Ajax days, he had no such issues with communication and whatever they say about ego. Interviews with his players also confirmed that. He did well during he first season with Manchester United, one thing people should know is that he has the best winning rates after Sir Alex Ferguson. That said, I'm one hundred percent certain he will be successful with Bayern Leverkusen.
You have players and coaches that work well in any team they play for or have responsibility for as a coach and you have those who work well only under very specific conditions. Ten Hag is not this universal puzzle piece that can make any team stronger. His communication issues are severe and there consequences thereof could perfectly be seen at the example of Manchester United.
He has had a few good years with Ajax Amsterdam, but tell me how many players were unsatisfied under Xabi Alonso and tell me how many players were unsatisfied at Manchester United under ten Hag? This can make a huge difference and what he had in Amsterdam was a pretty young team that was well managed with authority. The higher the level of the team and the more experience the players have, the less will that authority type of coaching style function to the benefit of the team.
Alonso is more the kind of Ancelotti guy while ten Hag is a bad version of Mourinho. Once these guys have had a place in one of the top leagues, they never get old and will always find a club giving them a contract. Ten Hag can now waste several more teams and yet he will find a new job.