Bayern Munich is still best club in Bundesliga even though they lost to Leverkusen. They had some ups and downs which allowed Leverkusen to take the lead. But I think Bayern will come back stronger next season because they learned from their mistakes. A big club like Bayern won't give up after one bad season. They will work harder and be back on top soon. Bayern hired new coach Kompaney but he did not do well in his last job so it is unclear if he can help Bayern improve. One thing is certain Leverkusen is likely to have another great season while Bayern still has a lot to prove.
By the way Leverkusen is doing well and Bayern Munich is struggling. Leverkusen has good players and good coach so they will likely keep doing well.
Next season is another opportunity for elite teams to try again. Bayern Munich had their worst season in previous Bundesliga campaign, they went home trophyless and we they fought through but couldn't achieve their aim. Bundesliga is a tough one and the possible elite clubs will exert tough job for success. You can't compare Bayer Leverkusen and Bayern Munich because the differences are huge. Bayern Munich have won major titles and Bayer Leverkusen are simply in their best form and winning the Bundesliga title with unbeaten.