The US supported General Duong Van Minh's coup against Ngo Dinh Diem .
He was supported from the beginning in 1955, to quote our leadership at the time, "...Diem's the only one we got!"
He was well known in Vietnam
A man that hated communism, and for that reason, was accepted by the Kennedy administration (in the beginning); See: Diem.
The United States.