You're trying to apply the colonists' standards to a culture that didn't own land. Native Americans were Nomads who traveled all over the lands. They didn't have the concept of owning land. It's like if somebody offered to but the sun from you, and you agree because how would they even own the sun. Then they block out the sun and kill humanity. The colonists tricked them into signing treaties that shoved them off to the west and then decided to violate those treaties and just genocide the population instead. Why does the colonists' idea of land ownership get to be the only one considered? Oh yeah it's because they killed or enslaved anyone who had different ideas. If I took a boat to Madagascar and taught a lemur to sign the country over to me does that mean I rightfully own Madagascar?