Most likely cause... Flat tire on towed, Driver of MH did not sense, tire (likely Right Front) shredded and the rim sparking along the road set fire to the towed.
I have never seen this actually happen but ..... I have dispatched a "high speed chase" where the driver of the work van was higher than a kite on multiple drugs, He ignored police requests to stop, and ran, Finally stop sticks were depoyed and flattened 3 of the 4 tires on the van as I recall. He continued and the tires were totally destroyed, the rims were throwing up a nice "Rooster tail" of sparks which eventually set the van afire.. STILL he refused to stop.. Finally the van died and troopers, at great risk to personal safety, were able to pull him from the remains of the van, 3rd degree burns and all. STILL he fought the troopers and had to be Maced before they could restrain him and transport him to hospital.
Drugs suck.
But that's why I think it was a flat tire.
I Have seen a towed where the driver of the MH did not know the tire had gone flat from some distance.. Thankfully he found out before the rubber was completly gone but.. The tire was toast.. I told him about TPMS.
Over half a million his motor home cost and he did not know about TPMS.
(Prevost, Very very very very nice rig)