This goes beyond one president, literally back to the founding of the country. It's not just some grudge held by this particular president. Even Obama has done some heinous shit to natives in regards to their land and rights.
The reservations have always been a set off moving goal posts that have been granted, moved around, and revoked—regardless of how 'good' or 'not good' the land is. The US government (read: capitalism, bc that's what it's always been) wants ALL the land.