That was my thought, too. Maybe the the big fire burned through control hydraulics on the right wing? It was flying level and stable with the big fire on the right wing for maybe 30 seconds, then lost lift on the right side and keeled over.
Probably right on the mark. At 0:40 it looks like the pilot kicked the rudder to get the wing up. You can see the yaw as the nose goes up but he has already lost it by then. Stalled it into a snap roll.
Prayers for the crew and their families.