Because the British promised them to give them whatever they desire.
That is the answer.
Hope this helps
He refers to his subordinate statement, he did not take the decisions, he only obeyed them. The moral implications of the policies of President Van Buren (and his predecessor Andrew Jackson) did not make those orders easy. But as a subordinate and not popularly elected, I had to obey them. Finding the best conditions for the Cherokee people was all he could do. In his instructions to the militia, he reminded them that any act of cruelty would become "an aberration to the generous sympathies of the American people" (many of whom, like John Quincy Adams, were against the transfer, blaming Southern politicians and the land usurpers ").
