Yeah, because any time you can fire a national-title-winning coach with a career record of 114-34 in the most savagely competitive conference in America, you know, dump that motherfucker.
LSU won something like the fifth-most games in the country during Miles' tenure, and it's not like they were falling off the map. They were 9-3 last year. The only sin that Les Miles committed was happening to be in the same conference as Nick Saban's Death Star at the wrong time. This is 100 percent driven by paranoia that LSU is falling behind Alabama, even though LSU is one of about four programs in the country that has been in the same zip code as Alabama for the last decade. Miles took over for Saban, who left a program in very good shape but not exactly juggernaut (went 9-3 and finished 16th in postseason poll his last year) and ably piloted the ship to the tune of five top-10 finishes, two national title game appearances, and one title.
Wiseasses always come out of the woodwork and say shit like "LSU is such a fabulous program, though, any coach can win there" or "With the talent on that roster, it's a crime that they were 9-3 last year, a good coach will get more out of that program." Two major problems with that train of thought. One, recruiting is a major part of college football coaching, and even if it's frustrating to watch a team full of blue-chip athletes struggle to execute, the ability to get those guys in the door still matters. There's no guarantee that Les' successor will be able to recruit nearly as well as the Mad Hatter. Second, lots of "fabulous programs" that looked like they'd be dominant forever don't really hold up. Early-2000's Miami looked like even more of a juggernaut; so did mid-2000's USC; so did mid-to-late-2000's Texas. Very few programs are actually so good that you can just set them on autopilot and churn out a consistent winner every year. Tennessee kicked Phil Fulmer to the curb after a down season and it took them eight friggin' years to recover, suffering through the Lane Kiffin and Derek Dooley disasters. This shit isn't as easy as it looks. LSU isn't some program where national title contention is a birthright; they were just "good" for most of the 1990's (finished in the final Top 25 twice in that span, never in the final Top 10).
His game management isn't the best. His offense is frustrating. LSU hasn't been able to develop a good QB. And you know what? He still piloted LSU to nearly unparalleled success in a brutally competitive SEC for a solid decade, never finishing with fewer than eight wins. Two years from now, when LSU gets their asses kicked by Arkansas and Ole Miss en route to a 5-7 finish, they will rue the day that they ran off the most successful coach in school history.