I think there's nothing wrong in aiming higher, they already have a bundesliga title and now they are anticipating the champions League which I think is good for them. It has been a very long time since they got to this point, at least there is nothing wrong in having huge aspirations. Perhaps they want to prove a point in European football after becoming runners up in the Europa League, they also want to try their luck in the champions league which would be a great improvement for the German side who were one of best teams in Europe last season.
Leverkusen won their title as the other teams weren't in good form therefore what they should have done is try to win it again so people don't say they only had a lucky break. After just a one season wonder, aiming for the champions league is too much for them. They don't have the players or experience to win it. The clubs that try to win the champions League are clubs that have a good previous seasons and not just one season wonders. They don't even have the strength in them to win the league title again this season. The champions league has Liverpool, Real Madrid that'll be challenging for it, Leverkusen should forget about that and focus more on winning their league games.