I am sort of confuse becouse this is phrased as one question (at first i thought you where talking about the recent fight about not putting in a pipeline but i relized you said why DID)
So i will split it into 2 Native americans fought for land becouse for one they needed a place to live and second they belived the great spirit wanted them to live where they did
It was "John O'Sullivan" who <span>entitled the phrase "manifest destiny," since he used this phrase to describe the vision that the US was "destined" to expand all the way to the Pacific Ocean. </span>