Why did President Truman side with France instead of keeping the promise to Vietnam as an independent country?

Truman had his hand's full: He just finished with WW2 (1945); just finished with "moving the whole human race into the atomic age" (Hiroshima/Nagasaki Atomic Bombings in 1945); and was then fighting the very first "hot" war with communist nations in Korea (1950-1953). Going on at the same time was the 1st Indochina War, aka the French Indochina War; the French were up against the communist backed Viet Minh...we were tied up in Korea, so Truman supplied the French with old WW2 equipment (propeller driven Hellcats, Bearcats, Corsairs), and WW2 US tanks...M-24 Chaffee light tanks, and WW2 half-tracks, plus small arms and some infantry armor (M-1 steel helmets). Korea ended in '53; the French war ended in '54.