Nothing like a real training class to give you preparation for an emergency. That's great to hear you didn't panic and maintained composure. I've taken the CHP's course on skid control for my job at the electric company and it's been some very valuable education, learning how to handle hydroplaning. Wish now they would have thrown in high speed blowout in a course for me too.
If I were to guess, I'd say you picked up a nail or other puncture that slowly lost air and heated the tire until it blew, never knowing what hit you.
Your situation is exactly why my wife won't drive our rig; she could pilot the thing with no problem up and until an emergency. I only can hope I'll react like you did. Mentally preparing is a big part.
