I don't think that it is impossible for Leverkusen to win Bundesliga this new season but it will be difficult because if you look at it from this angle, only Bayern Munich have won it back to back and is still the favorite to win the league despite the challenge that they are having in bringing Kompany to be the new caich of the club.
Leverkusen will be playing in UCL which if they don't improve their performance amd stay strong when they get lose matches it can affect their performance. Last season was so smooth for them and all their mentality was winning with no lose, giving them more confidence and motivation till the last match which they lost to Atalanta. Losing a match in UCL can affect their performance in Bundesliga.
You have a good point and concern about Leverkusen because those clubs that do not win often but just did the underdog thing to win often disappoint the expectation of replicating it. Just like when Nopoli won Seria A in the 2022/2023 season, neither the club nor their best striker was able to replicate the success. But I still have a high degree of belief and trust in Leverkusen, they may deliver again, or at least finish at the second spot this coming season. My reasons are simple, the same coach will defend the title next season and nothing has so far significantly changed in the team compared to the last season.
Besides, Bundesliga clubs have not been so challenging for many seasons ago, it's either a certain club or 2-3 clubs performed well and the others performed woefully, which is what is mostly giving Bayern Munich and Dortmund some advantages over the years. But with a viable contender like Leverkusen and their brilliant team in play again, I see it differently. Bayen has not also made a huge change that would warrant fear, and neither is Dortmund. The two teams are the major concern I could see for Leverkusen, so I expect something similar to that of last season, and it's not a crime for an underdog club to replicate its winning, especially when they stay strong as I see with the current Leverkusen.
