I call it "The clue everyone missed". That isn't a vapor cloud expanding outward from a surface explosion. It's a vapor cloud blasting straight up, in a separate location from the explosion (I estimate 150ish yards away).
I've been away from this site for a while, and missed discussion of this event. I could not find this oddity covered, so for anyone interested, I explain it in the video below, shown from a different angle.
It's abundantly clear there was an underground component to the explosion, begging the question; what was below the surface?