When he went public with his story...
in the New York Times, it was only natural that someone asked, "Who sent this clueless idiot to Niger?" What possible expertise did he bring to the investigation, except perhaps his talent for sitting around drinking tea? Why does anyone in the CIA responsible for sending him still have a job?
When it turned out to be his wife (as documented by the Senate Intelligence Committee report) that sent him, is it revenge to point out the fact? She had not been covert in over 5 years, so the law about revealing a covert agent didn't apply. Wilson has been exposed as a liar of the first order.