I get why both Solich and Pelini were let go.
Tom Osbourne went 49-2 in his last four seasons, had 3 undefeated seasons and won 2 national titles. Talk about going out on top. Solich had a few really good seasons, but going 7-7 and 9-3 in his last 2 years was certain to bring the pitchforks out when fans were used to literally having undefeated seasons on the regular.
Pelini never lost less than 4 games (aside from the year they fired him). Plus, in every one of his last 6 years there his teams finished below (often far below) their preseason polling. Fair or not, that's going to generate a lot of fan frustration. I think if he had a signature year where they went, say, 11-2 and won a major bowl, that might have given him a longer leash.
Most importantly, Scott Frost sucks so ha-ha-ha.