Leverkusen are starting over. Xabi Alonso and Erik ten Hag have different systems you know. They don't adopt the same game plan. So it would take some time to get better...
The championship odds:
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Bayern Munich: 1.29
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Leverkusen: 8.50
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Dortmund: 11.00
As a result, it would be a big surprise even if Leverkusen win the Bundesliga this season.

The board would expect ten Hag to finish in top 4 at worst. The Champions League qualification must be a crucial target at this point.
Winning the Bundesliga? It would make him the king there for sure...
Bayern munich are already strong contenders to win the bundesliga this season. there’s little reason to expect leverkusen to turn things around, as ETH hasn’t made a significant impact on them. meanwhile, dortmund are struggling just to maintain a top-five finish. so, it seems clear that bayern munich will win the bundesliga with relative ease.