According to the updated Avherald article, they had a hard landing, and damaged the landing gear. That caused the airplane to veer off the runway, break in two, and burst into flames.
"The undercarriage of the aircraft was severly damaged in the landing causing the airplane to veer off the runway. The impact caused the fire on board.
The NTSB reported on Jul 31st, that the aircraft "reportedly caught fire after a hard landing at the King Khalid International Airport, Riyadh, Saudi Arabia". "Some observers on the ground claim the aircraft was trailing smoke while on approach, indicating a fire on board prior to landing, including officials at the airport.
"Observers on the ground said, that the airplane was already trailing smoke while on final approach.""Saudi Arabia's Civil Aviation Authority (GACA) confirmed on Jul 27th the crew arriving from Frankfurt (Germany) declared emergency reporting a cargo fire inside the aircraft while on approach and landed at 11:38L (08:38Z). An investigation is under way." "Officials of Riyadh Airport said on Jul 29th, that the crew reported a cargo fire while on approach, emergency services immediately deployed and observed the airplane arrive in thick black smoke before the airplane touched down on the runway."Lufthansa disagrees...
"Lufthansa Cargo said on Jul 30th, that they have no indication of an inflight fire."All of the above is from the updated Avherald article:
http://avherald.com/h?article=42edca16&opt=0