What is the primary cause of brake fade or brake failure on a long or steep downgrade?

49 CFR 383.111(b)(7)(i) – Proper braking techniques (knowledge test requirement); AAMVA CDL Manual, Section 5, subsection 5.4.5

Brake fade on mountain grades is a leading cause of runaway commercial vehicle crashes. Knowing that heat, not a single bad component, is what kills your brakes tells you the fix is prevention: use the engine to do the slowing down before you ever need the brakes to bail you out.