Bochum has often been an obstacle to wins for the top teams and this time they managed to draw against Union Berlin away. Surely this is not the result that Union Berlin wanted because they could not get an additional three important points so they could be closer to Dortmund. On the other hand, Bochum must win the game next week to be safer from the relegation zone. A few notes added to the results of this match, previously Bochum managed to beat Leipzig and also held Frankfurt and lost only 1 time in the last 5 matches of the bundesliga, so I think Bochum has had quite significant results in its last few matches.
I don't know how the results of the match between Dortmund and Bayern Munich got a draw in their respective matches, even though this was an opportunity for them to widen the points. Union Berlin also missed a good chance to catch Dortmund points, even if they win against Bochum they are closer to Dortmund, but as you said Bochum always makes it difficult for top teams in crucial matches.
Bonchum's motivation is even greater to win the remaining few matches ahead, because they have to get points to avoid the relegation zone and currently Boncum's points are still not safe because they have the potential to be chased by those ranked below them.