why was andrew johnson impeached but not convicted?

why was andrew johnson impeached but not convicted?
The primary charge against Johnson was that he had violated the Tenure of Office Act, passed by Congress in March 1867 over Johnson's veto. ... Specifically, he had removed from office Edwin Stanton, the secretary of war whom the act was largely designed to protect.
Full answer in: en.wikipedia.org
What was the vote on Andrew Johnson's impeachment?
The House Committee on Reconstruction reported resolution of impeachment against Johnson. House voted 126 to 47 to impeach Johnson of high crimes and misdemeanors.
Full answer in: www.senate.gov
Why was Andrew Johnson not convicted?
The senators voted 35 guilty and 19 not guilty on the second article of impeachment, a charge related to his violation of the Tenure of Office Act in the previous year. ... Because both votes fell short–by one vote–of the two-thirds majority needed to convict Johnson, he was judged not guilty and remained in office.
Full answer in: www.history.com