It seems that what you say is true, that Leipzig is no longer focusing on the champions league because they have little hope from the two matches they have passed before, and choose to secure their position in the domestic league, it can be used as a reason why Leipzig is much more enthusiastic in the Bundes league, on the other hand Bayer Munich, Bayer Leverkusen, Dortmund and Stuttgart are fighting for their names in the champions league, if their concentration is divided it will drain their energy and that is an opportunity for teams that focus on the domestic league.
When a team sense they have little or almost no chance at a league game, the best thing they do is to redirect their priority because that's the best thing to do, if you know you at the moment don't have the experience to handle that which is before you considering the nature of the champions league, its best to just face that which you have got some level of certainty around and maybe that's exactly what Leipzig is doin currently, in the Bundesliga even if Leipzig cannot be bale to win the league title, they are sure they will finish well and that is the most important as they are inexperienced for UCL.