It looked to me like intermittant lock-ups? Retreads can come-apart in odd ways. I just haven't seen that in a failure. I remember as kid taking a pair of retreads on an old Desoto (with a great hemi-engine) out on an uncrowded, newish Interstate highway one Summer. I had that car up to 110 mph. When I pulled-up to an overpass to turn around, the rubber on the tires scared me alot. No chunks out, but pretty soft rubber that was too close to touchy-feely :^)))

My guess is that your brake failure wasn't an instant even, but over time. If you get a failure in a linked system, you can heat-up the break fluid or cause increased pressure in the line, which causes increased heat because the calipers get "pinched".

Did you notice any difference in the pedal feel?

I think you were pretty lucky, Greg. A lock-up on one side can cause a lot of not-good things. There's a huge difference between towing at, say, 55-60 mph; and trying to roar along at 80 mph. The forces increase by the squares of differences in speed. (Maybe the fourth power, for some things, but my physics isn't what it used to be.)