Bill Snyder's predecessor, Stan Parrish was 2-30-1
Parrish's predecessor had ONE mediocre winning year in eight seasons, earning KSU with their FIRST bowl bid EVER ('82). The other 7 seasons were 4-7 or worse.
Snyder inherited what Sports Illustrated called the worst program in Division I at the time. He concluded his first tenure as HC by winning 11 games in 6 of his final 9 seasons, an amazing fact you neglected to mention.
When you have an 11-13 career record against the Sooners and Horns at a perennial loser like KSU was, you can leave when you want. Yet, he appropriately retired when he realized he wasn't meeting his expectations.
Comparing Fulmer's situation to Snyder's is silly. The standards aren't remotely similar.