The recent win of AJ Styles over Kevin Owens for the US Title was a late decision but it is unclear at the moment why this was done according to Dave Meltzer on Wrestling Observer Radio. Meltzer suggests that it was highly unlikely that it was just a booking decision but rather there must have been a deeper and specific reason why this was done. He did speculate however that a rare event like this could likely happen if Owens were to be injured.
The other interesting news here is that since it was a Raw house show and to have two Smackdown superstars compete and then have the title change hands just days before a live TV event raises eyebrows and hypes up the win even more. As soon as more information is available on this matter it will become open and it will be reported.
Source: Wrestling Observer Radio