I am not sure the Leverkusen players have lost confidence this season, but I do believe the majority of them are tired. They were undefeated in all competitions last season, losing only to Atalanta in the Europa League final. It wasn't simple for a team to be undefeated in one season and then perform at their best the following season. Though their performance is still not bad this season, they currently sit second in the league.
Bayer Leverkusen must realize that winning a trophy is not their thing this season, however, they may still win the DFB Pokal this season. One of the things is that, based on Leverkusen's performance this season, I don't think they will survive a season without Florian Wirtz, if he had been available for the second leg, I would have expected Leverkusen to score at least one goal, both in the first and second legs, Bayern Munich did not take it easy on them.
The explanation for this is that Bayer Leverkusen done have the same quality they showed last season. They have a very awful defence that made constant blunders, which has made them concede cheap goals. Injuries also affected the club and they also failed to get more players to coverup or safe as backups for wornout players.
Frankly speaking, Die Werkself should focus on remaining in the top spot so that they can play on the UCL next season. They should also prepare to get new players and let unwanted players leave to enable them to get a solid team for next season.