Kevin Costner went out with a bang - and a shove - on Yellowstone. Troubling new allegations have bubbled up surrounding the Oscar winner's tumultuous exit from the acclaimed Western drama. If you didn't know, Kevin left Yellowstone in 2023, announcing at the time he would not return for the second half of the fifth season due to scheduling conflicts. Supposedly this was all over his commitment to his passion project, the multi-part Horizon: An American Saga. But there's long been speculation there was more to it.