Bill Clinton did fire him, he just didn’t know that the other Clinton had just killed him...
For folks who weren't around (like you, apparently) Hillary was on her way back from Hawaii with a stop at some garden club in California on the morning of July 20. According to the official time-line, she did learn about Vince while en-route to DC before the Slickster who was in the WH all evening.
Hillary made an unscheduled stop in Little Rock on her way back from California that evening (to bake some cookies, no doubt).
I believe the reason Sessions was fired was to clear the way into keeping the FBI out of any investigation into the death for six months, or so, in favor of the Mighty Park Police.
ML/NJ