Far be it for me to criticize anything Nick Viall does on his season of The Bachelor, because everyone goes about relationships differently, but I do have to draw the line somewhere. Why was Nick smiling while eliminating Corinne on The Bachelor? The Bachelor star and future Dancing with the Stars contestant hasn't gone on the record about this moment, so we're left to speculate as to why he looked so amused and almost seemed to laugh at times, during his goodbye with the polarizing blonde. But luckily, speculation is one of the things I do best, so I'd like to put forth a theory: I think it was a combination of Nick feeling awkward and not really taking Corinne seriously, either as a partner or as a competitor.
Let's talk about the feeling awkward thing first. Having observed Nick throughout this season, I've noticed that he seems to have a tendency to smile or even laugh when he doesn't know what else to do, and he was in that situation a lot with Corinne. It happened when she took her bathing suit top off during that photoshoot in the swimming pool, it happened when she showed up in a trench coat with a can of whipped cream for their alone time, it happened when she climbed on top of him in the bounce house, and it happened a whole bunch when she was buying him clothing during Hometowns. I think smiling is just something Nick tends to revert to in certain situations, much like covering his mouth with his hands and mumbling in intimate moments.
And as for the second part, after watching the video of Corinne's departure a couple times, I think Nick was genuinely surprised that she was having such an emotional reaction to her elimination, because I don't think he realized how invested she actually was. I've always sensed that Nick feels a deeper — let's say more mature bond — with the other three remaining women, Rachel, Raven, and Vanessa.
That doesn't mean I don't think Nick and Corinne would have been a good couple — by the end there, I actually thought they were the best match — but I don't think Nick was quite hip to that idea. Based on his reaction when she was actually upset at being sent home, I think he might have thought Corinne was there just to have a good time, and that she didn't have serious, deep feelings for him. That would explain why, when faced with her emotions, he reverted to his traditional response to discomfort: smiling.
And just to add another layer to this, I think Nick genuinely liked being around Corinne, and her general demeanor really made him smile. So when she apologized and asked if she'd done something wrong, he seemed really eager to reassure her, and the positivity that he felt toward her came bubbling out as a smile and a laugh. At least, that's the vibe I got from viewing the footage 4 million times, but feel free to watch Corinne's Bachelor goodbye a few more times yourself, and come to your own conclusions.