They screaed to stand against Leverkusen because they saw the perfect performance from this team and the performance of Leverkusen during the last season was well enough which made this team unbeaten during the games they had in the Bundesliga. However they recently lost a game because of a comeback but still, Leverkusen is scary for any team in the Bundesliga.
I think Leverkusen fans also expect to see much better performance from them because they still want to see their team win the title at the end of the season.
I think Bayer will have a completely different season, first of all because of the heavy workload on the players in the Champions League, to some extent because the Champions League will use a new format, which will increase the number of games. In the next round they will go to visit Hoffenheim, and after that the Champions League matches will begin, and we will have to see how the results in the Bundesliga can change from the end of September. It seems to me that Bayern is more accustomed to this regime, so they will cope with it better.