Why was andrew johnson charged with breaking the tenure or office act

The House's primary charge against Johnson was violation of the Tenure of Office Act , passed by the U.S. Congress in March 1867 , over the President's veto. ... (Earlier, while the Congress was not in session, Johnson had suspended Stanton and appointed General Ulysses S . Grant as Secretary of War ad interim.

The majority of both parties voted in favor of the bill all senate republicans voted in favor of the bill