I don’t see how “why?” makes any difference. There is no serious argument that the US gov’t does not own the land. There is no evidence that the US gov’t reneged on a contract to let him graze cattle there. It may very well be that the gov’t has a stupid or bad reason for stopping grazing, but that has nothing to do with its right to do so.
Just a reminder, the federal government does not have rights - it has powers.
Somebody wants him off that land, and it's costing us a bunch of money to do it for no good reason that I can see.