I'm catching up here so excuse me if this has already been said but is the failure only on the left front, what's the pad thickness of the right front pads?
Could it be a sticky LF piston from a bad or stressed piston seal leading to brake drag? That might explain the red hot rotor, deformed caliper/pads and blown line. Even the slighted bit of drag leads to escalating heat---more heat, more drag, more heat. It appears that the system had no chance to shed it.
Did you notice any brake drag on turn-in?