Basically he wanted to improve his NFL stock because being a projected 2nd rounder wasn't good enough.

Quote from the article:

That would represent a continuation of Etienne’s master plan to improve his NFL draft stock; he received a second-round draft grade.

“I just felt like I could come back and disprove that grade,” Etienne said. “Leaving for the second round never was in my mind. I feel like I could do so much better than that. The NFL’s going to be there, so I mean I wasn’t leaving for no second-round draft grade.”