Why did native American leaders agree to give up most of their land in what is now Ohio?

The Native Americans consented to formally surrender the vast majority of Ohio and parts of the remainder of the Northwest Territory to the Americans; the Native Americans additionally consented to let the Americans gently settle in those grounds without dread of assault. In return, the Americans would pay the Native Americans one singular amount and an extra money each year in installment for the land. The Americans likewise concurred that they would not formally settle past the outskirts built up by the arrangement, and they would keep on enabling the Native Americans to chase the grounds they had surrendered.