Why was the Greenwood community destroyed as noted in the nonfiction book, Unspeakable: The Tulsa Race Massacre?

Greenwood, a prosperous Black community located in Tulsa, Oklahoma was known for its Black-owned businesses, churches, hospitals, a school system for Blacks, and fine homes. In 1921, the community was destroyed by Whites after a Black man was accused of assaulting a White woman. Greenwood was looted and burned.