As I recall, Bohl was fired as the DC by Frank Solich after the Huskers went 6-7 in 2002, a season in which the defense regressed from the #8 defense in the country to #56. The secondary coach and DE coach were also fired.
Solich was fired less than a year later, after a 9-3 regular season. Bo Pelini was the interim coach for the bowl game win over Michigan State.
Not a big difference, but they were 7-7 in 2002. They finished the regular season at 7-6 and lost to Eli Manning in the Independence Bowl. I think the firings happened prior to the bowl game, but it’s been too long for me to remember.
There were lots of unsubstantiated rumors about Bohl and Solich that came out after they were fired. I never gave them much credence and didn’t really think they were all that relevant. More or less, it seemed like a convenient excuse to further justify their dismissal.