Because there are no legal grounds to do so. This has the same merit as asking why your grandmother hasn't been charged with Genocide.
He resigned before they could start impeachment.
TRUE
Nixon?
Britain and France tried to avoid war by accepting the demands of Germany through appeasement.
They appeased the dictator by accepting his demands in an effort to avoid war.
It is called acquiescing or capitulating.
President Richard M. Nixon.
They tried to avoid war with Germany by agreeing to some of its demands .
Richard Nixon was not put on trial. He resigned in August of 1974 to avoid impeachment, which is the rough equivalent of indictment.
This is called Appeasement. It means giving into commands in order to avoid a fight from someone of higher rank.
Appeasement
Richard Nixon was not impeached. Three articles of impeachment were drafted by Congress but the case never proceeded. Nixon resigned August 8th, 1974 to make impeachment a moot point and Ford's pardon of Nixon on September 8th, 1974 made indictment impossible.