Some people just roll into collapse & submit. If your life is shit, you have the option of trying to blend it out or succumb to it and be miserable. Some people become overly optimistic because it's the better, less stressful solution.
Plus, he really IS kinda dumb, so that paired with deciding to see everything positive can make for a really weird combo. XD
One way or another, I think he's more dumb-y-fied for story's sake anyway. It would likely be less weird to see if he was a highschool kid that lived with granny or something. You know, having a doting figure in life that shelters him? Plus, the younger, the dumber. That's also making it less weird than it being portrayed in a college guy.
yeomin kinda dumb but i can’t blame him