I feel like the reason why you regret the decision is because deep down you’ve always wanted to mingle with people there but never got the chance to because you were too stuck in your own box. And by being too attached to your own comfort zone, it made you decide to transfer.
Part of the reason why you’re feeling like you’ve made a mistake is because you’re thinking that you’ve switched to a not so Big Ten from a Big Ten school, and I know it gets frustrating when people react to those situations without considering other factors that made you do what you did.
I used to brag about getting scholarships from a private university only to find out that I still couldn’t afford it, and so I had to go to a community college. It was not fun and it made me feel less than the rest of my batchmates who fled to their desired universities. However, I learned to love it overtime and enjoyed the perks of being in a “less prestigious” college.
You’ve made this decision, and I know it sucks right now, but you’ll learn to appreciate it. Stop guilt tripping yourself over the possible reasons why you shouldn’t have left along with people’s reactions. You’ve had your reasons and made a decision, and you gotta stick with it, or else you’ll be going around in circles wasting time. You don’t want to get caught in that habit.