Traffic Surprise!

I will never understand traffic as long as I live. I was told to leave work early, around 5:30pm, which is basically the kiss of death of traffic time in the Sacramento area. However, there were only brief moments of slowing down instead of full-blown stop dead traffic. Why? It is a weekday... and I'm pretty sure I've driven on the 80 freeway on a Wednesday at 5:30pm before and gotten stuck like molasses in winter time. I'm baffled. BUT, I DID get home much quicker than expected, and that's always fine by me.