As we saw in the clip, even though he was clearly intoxicated, Max Greenfield’s Lucas was able to notice a big problem when drunk Dean started randomly saying Rory’s name during his bachelor celebration.
I mean, they were talking about getting strippers who were maybe also prostitutes!
Of course, Dean wasn’t over Rory, but felt the need to move on, so he started dating Lindsay, and quickly proposed to her, even though it was clear that he was still in love with Rory.