Why did John move to Bloomington from Seymour?

This part of a 1986 LA Times article (I'll post the whole piece shortly) might help answer your question:

The sign on the front gate of Mellencamp's gray, two-story home just off Highway 46 isn't the friendly salutation that you'd expect from someone whose songs celebrate the virtues of small town life:

NO SOLICITING. NO TRESPASSING. IF NOT INVITED, DON'T PUSH THE BUTTON.

Mellencamp, 34, says he didn't want to put up the sign . . . or the imposing iron gate . . . or the expensive electronic monitoring system so he can see who's coming up his driveway. But too many fans were showing up outside and he was worried about his wife and three daughters during the weeks that he's on tour.

But he didn't have any reservations about putting 45 miles between himself and Seymour, the town where he was born.

Sure, Mellencamp often returns to Seymour on Sundays to play touch football with band members and old high school chums, like Weasel and Bo. He'll even probably be buried there--near his grandfather, Speck Mellencamp, whose plot is on a cemetery slope overlooking the family home.

Until then, however, Mellencamp will only be a visitor in Seymour. He left that small town for a reason and that reason still applies.

"It just got too weird in Seymour . . . too suffocating," he said flatly, sitting at his kitchen table. "When you are making records, you got people in the town who either love you or they hate you. I could never go back there (to live). It's too small . . . too busy-body."