Indeed have inconsistent performance in this season, Bayern Leverkusen almost reach the top standings with four points remaining from Bayern Munich, last defeated match from Mainz make Bayern get their first defeating in domestic league and looks not comfortable yet their first place behind Bayern Leverkusen almost reach first standings.
Bayern Munich looks difficult scoring many goals last match after Harry Kane absent and he most important players in this season behind 14 goals contributing in domestic league.
Bundesliga have long break for upcoming match due Christmas day and all teams have opportunity get recovery back their teams and prepare for recruiting new players, games week 15 will begin middle week next months and all teams can focus for signing new players when January window transfer opening, Bayern looks need new forward how to anticipation when Harry Kane absent.
Considering how they have been lately, I would say that it's clear they are not really doing anything crazy, we are talking about a team that did way too much last season so it is normal for Leverkusen to be not as great as last season. They were unbeaten all season long until Atalanta game, went like 51-52 games without a single loss, and that is not a normal thing at all, we are talking about something unusual there, and that is why I do not think that we are going to see them do the same thing ever again, not even Bayern did that on their best prime period.
However, just because they are not unbeaten, doesn't mean that they can't win the league, even if Bayern loses one game, like Leipzig this weekend lets say, that would put the difference at only one point. I am not saying Leverkusen will win the league or anything, I am just saying they are not that far away and could have a chance, so they are not doing that terrible, and finishing second behind Bayern isn't a bad result.