The president's 2012 post came back to haunt him after he announced Mark Meadows would replace Mick Mulvaney in the role.
Trump shows more interest in this subject than "literally any other" in the presidential portfolio, the "Late Night" host noted.
Vice President Mike Pence swore in the former chairman of the Republican National Committee.
Kelly was named chief of staff in July 2017.
The former FBI director mentioned the crowd-size kerfuffle as an example of Trump lying in private as well as in public.
“Kellyanne is the number one leaker”. A new book on Trump’s presidency claims Kellyanne Conway regularly slips White House secrets to the press.
There have been several high-profile departures from the Trump administration in the year since the president took office.
“The last thing I wanted to do was walk away from one of the great honors of my life," Kelly said about his position at the Department of Homeland Security.
A revolving door never spun so fast.