Why did Bill Clinton leave office?

Bill Clinton left office because he served two four-year terms and could not run for a third term.

He was impeached for perjury, obstruction of justice, perversion of power by the (Republican) Congress on Dec. 19, 1998, then he was 'acquitted' by the (Democratic) Senate on Feb. 12, 1999. the following year. Thus, he was not removed from office.