Yes it's true that Leverkusen has sold some of their players but they are also recruiting before the season starts I believe that they have players that they have pencilled down to buy even though that Leverkusen may not be necessarily as tough as before I will still go for them to challenge Leverkusen for the title race
I think making changes by the time is a positive thinking to rise up and up. If Bayern Leverkusen sold their players then at the same time they also buy new players for the betterment of their team. For now Bayern Leverkusen's only struggle is to win the Bundesliga title. And to fulfill this desire they changed their coach as well. But the new coach is also suffering from his criticism phase due to his poor performance in Manchester United. So achieving new milestones depends on the coach and other team. Strategy should be outclassed to make the win possible . Because the coach is under pressure and the expectations are also like there is no chance of any mistakes. This is necessary for both the team and the coach's career as well.