Because it could be that in the first half Dortmund tried to study the opponent's game first and waited for their stamina to decline and when entering the second half, Dortmund showed their original game. In a favourable situation when the opponent has no way to catch up. The flow of the game has been completely controlled and now Dortmund is in the temporary runner-up position, Leverkusen has 1 match that can be utilised, but unfortunately Bayern Munich is in the best condition. Today's big game will measure how different these two are. Bayern Munich are on a mission for revenge, so I hope Xabi Alonso is really preparing everything.
Xabi Alonso always prepares everything in facing tougher rivals including Bayern Munich this season where they will also compete today at the Allianz Arena. While Dortmund who were behind by one goal in the first half in today's home game, I think it is also quite right with the reasons you stated because Dortmund is a team that knows when to attack its opponent in a more crucial condition so that in the second half Dortmund successfully scored three more goals and that has made it win at home in today's match.