It's a good one they want to make a change of their coach but it could be that's not allthat it is to their issue of poor performance and productivity, although they have not explored their policy of selling of their best players too often recently but then it's possible the long term after effect is dawn on them now and they are looking to explore options to fix the team, mea while a build up all over again is what I think will be best for them currently. Good thing is they can afford a good coach if they get one.
They have to change the pattern and may not sell some important players even though the price offered is high. Changing the coach is also not fully successful because sometimes this will actually make the conditions worse. They need to rebuild the team to be stronger and do not necessarily sell every player who shows an increase in performance for reasons of profit. If you want to rebuild the team to be stronger then it takes time because it is not easy to achieve success in a short time.
They should have stopped that a long time ago, many players are valuable and have good potential in their development but they sell them which ultimately makes them not so good in the competition in the bundes league, even they can be lost by Leverkusen who pioneered more recently in the ranks of the top competition for the trophy, and they can only be runners up even when Bayern Munich previously experienced a decline in performance, this certainly needs to be questioned and a lot must be evaluated from how investment in the team itself produces better results, and yes they need time if they reconstruct the players they have today to be able to compete much better.