"Rumblings"? "Rumblings" of competition wouldn't deter a determined suitor.
Here's I think the true explanation. These deals are extremely complex legally. UConn had sold a wide range of Tier 3 TV rights to SNY, IMG, etc; ACC had sold all rights to ACC league home games to ESPN/Raycom. These contracts have to be reconciled. UConn would be a complex and lengthy negotiation for the ACC, and UConn would throughout the negotiation be going back to its contract partners and also the B1G to look for better offers and ways to reconcile terms to its advantage. Louisville on the other hand would sign whatever proposal the ACC put forth on the dotted line. All we need to assume is that the ACC wanted to move quickly, and they would pick Louisville.