When we have a look at where Union has lost points so far, we can say Union is very strong at home but having some difficulties away.
Oh yaa, true, from the match statistics, it seems that Berlin has had some difficulties and even lost several times when playing away. Could this be one of the mental reasons for the players? Because, when they are at home, they can really play very well, even being able to hold Bayern to a draw. But when in the opponent's cage, then they have lost or drawn several times. Sometimes the mentality of the players really determines the outcome of the game.
Union didn't wanna lose points from bochum. This is football when everything still remain unpredictable. Don't forget another bad result by big team from another league.
Of course, whoever the club doesn't want to lose points. However, I think the answer from @1miau really makes sense from the above, that Berlin often has a hard time playing away. Maybe there was another factor in the defeat. And for sure, I really salute Bochum's struggle so that they can beat the leader of the standings.