Over and over and for many years now we see RV's going up in flames.
The better percentage of them are DP's where the engine catches fire.
This looks like just that. If the toads tires were locked up and/or smoking or was on fire 'someone' on the road would have flagged him down in time to unhook it.
The amount of damage to the interior of the back of the MH suggests the DP engine caught fire first and then the toad.
Once that engine and MH went up in flames no one is going to be able to get near that tow bar to unhook the toad.