Crennel took over with three games left in the 2011 season after general manager Scott Pioli fired Todd Haley.
Kansas City will have the No. 1 pick in the NFL draft as a result of having one of the worst seasons in its 53-year history.
The only other time the Chiefs finished 2-14 was 2008, the year before Pioli was hired.
“I am embarrassed by the poor product we gave our fans this season, and I believe we have no choice but to move the franchise in a different direction,” Chiefs chairman Clark Hunt said in a statement.
Gailey, the former Dallas Cowboys coach, compiled a 16-32 record in his three seasons in Buffalo, never doing better than 6-10.
“This will probably be, and I say probably, but I think it will be the first place that’s ever fired me that I’ll pull for,” Gailey said.
Smith and the Bears went 10-6 this season and just missed a playoff spot, but Chicago started 7-1 this year and has struggled to put together a productive offense throughout Smith’s tenure. His record was 81-63 with the Bears, and he took them to one Super Bowl loss and to one NFC championship game defeat. Receiver and kick return standout Devin Hester was bitter about Smith’s firing.
“The media, the false fans, you all got what you all wanted,” Hester said as he cleared out his locker. “The majority of you all wanted him out. As players, we wanted him in. I guess the fans — the false fans — outruled us. I thought he was a great coach, probably one of the best coaches I’ve ever been around.”