In addition to what everyone else posted here, it was in all the articles that most coaches stopped recruiting him because they assumed he was going to follow his brother to UTEP. On top of that he is blowing up this spring so I assume a lot of big time programs would have offered him after seeing him this spring. He wasn't as good last year. Rudy Gay had the same thing happen to him the spring of his junior year.
On top of the comment from Jerry Meyer someone posted above, here is another comment after Hamilton's commitment:
Eric Bossi, Rivals.com recruiting analyst: "Terrific pickup for UConn. Hamilton will 100% be a five-star in rankings update." (FYI, 5 stars is top 25)
Believe me, this is a huge commitment for Ollie and UConn. He went all the way across the country and got a 5 star player to commit to a school that has a new coach, is in a new watered down conference and who, honestly, has struggled to get the top rated recruits very recently. This is a big momentum builder.