I think the reason for Leverkusen to drop form earlier this season is because they over work themselves as of last season and this season they perform poorly and could not even get close to the league leaders due to fatigue and lack of player rotation, they needed to rest but this season came with a lot of work load. They manage to get everything in order to start up a better display that's why they are where they are and you should be worried about Bayern Munich because I believe they're still going to make that mistake you said they won't want to make. Leverkusen can try to catch up with Bayern Munich and the league is still open not to see Bayern Munich as the favorite to win it but we should consider other teams in the top 4 on the log as well, the Leverkusen have hope of changing the initiative.
Leverkusen have performed as expected this season, it's just that the fans have expected too much of them. Seeing Leverkusen being able to occupy the runner-up position in the standings at this time, it is something to be grateful for, because basically it is very difficult to repeat the same performance as they did last season. It is always not easy to compete with Bayern Munich, Kompany squad is a team that has long dominated the Bundesliga, the depth of their squad is much better than all the other contestants.
The burden borne by Xabi Alonso and the players is also much heavier this season, because they have to compete in the Champions League. So if Leverkusen fails to defend the Bundesliga and DFB Pokal trophies this season, I think it is understandable. However, luck may be on Leverkusen side again, they still have many opportunities to overtake Bayern Munich, because the season is still very long.