To be really honest, I didn't think it either until I went to check the score. This is too much for Bayern Munich to handle; imagine a 5-1 lead. Frankfurt is a small Bundesliga team, and while I understand that games can change, I believe that Bayern Munich didn't want to win. All of their strong players are on the pitch, and none of them can defeat Frankfurt. This is also an indication that Bayern Munich will not win the season title because of the way leverkusen are playing and the fact that they have more points than Bayern Munich. It seems like Bayern Munich has run out of things to do.
Leverkusen hasn't lost to any team yet this season because they always take each game seriously and that's why they maintain winning streaks. The team has a good coach and players communicate well with him. Last season, they were able to qualify for the Europa League, and this season, I believe they will win both the Bundesliga and qualify to the Champion League.
Munich's last Bundesliga game against Frankfurt was a huge indictment on their status, they were believed to be a better side but one way or the other, Frankfurt was able to gain the 3points and also keep the goal margins too. Added to the fact that they were the visitors in the game, Bayern still would have strived to do better and get a tangible result, they really underestimated Frankfurt and they paid for it.
Their loss however has cost them a reduction in points too and Leverkusen's draw helped them maintain point gaps too. Tuchel's team need to level up as the bait is no longer for the sluggish. Leverkusen has a target and from the beginning of the season till now, they've ensured that they maintain the competitiveness and fight to get the trophy. Although this is just the first half of the season, there's still time for Munich to get back on track and make corrections, their next game would be looked out for to mark either a progress or a decline in their race.