It's always what Dortmund is known for; I'm not sure why they don't keep players for long; once a player expresses an interest in leaving the team, they just let him go without considering how the fans will feel or the team's performance.
That's how they let their best striker, Erling Haaland, leave last season, and now they've lost form because they're not competitive this season, so instead of buying more players, they want to sell more.
This is the way Dortmund do things, if a player doesn't want to play for them anymore I think they are thinking that player would surely have a hardtime playing and will surely make mistakes because he doesn't have that urge in continuing anymore so he likely Dortmund will need to eventually cut their ties on them, and getting large money over that player's sale, well Dortmund is pretty much well known in doing such things when certain players would have a large value in them it is an opportunity for them to cash in big amounts,
Bayern Munich can still get it right to win this trophy because, we have see some teams like this in other competitions that turn to first position at the end of the tournament which, something like that can still happen in this tournament. Despite their starting in this season look poor, I believe they will do everything possible to work together as a team to make their fans feel good by achieving the trophy with different strategies people have never experience from them since the beginning of this tournament.
They can surely get it right, I think they got plenty of time to settle their score to get themselves a goalkeeper to fit the shoe of Manuel Neuer, and in Sadio Mane's case I think they need to hold on until Mane returns from his injuries, but surely there is no given time of his return so it's likely not a serious one, and may return anytime the season starts back up again, and maybe they can still hold on even with Leroy Sane as their Winger, and Sarge Gnabry will likely be another while Choupo Moting and Jamal Musiala for additional offense, I think they can still handle the situation at hand,