In the couple of years before ATT bought DirectTV, DTV put on a few dog and pony shows for ATT and the talk back then was ATT was interested in the contracts for content. Their U-verse TV didn't have enough subscribers to have much clout when negotiating the contracts.
Would they have gotten more UVerseTV subscribers by going all fiber than buying DTV? Their boxes and guide would have needed to been updated. Even updating to all fiber they would have to up the bitrate to handle 4K.