BRUpax
I understand your concern but I would suspect from the description of events and the pics available that the engine was not 'on fire' but had what is known in the trade as a hot gas leak. This is when any one of a number of seals or joints lets go and allows a jet of v hot air to escape into the nacelle. This will usually trigger a fire warning system and in single engined aeroplanes the drill is to throttle back to idle and wait for a mo to see if the warning goes away - if it does then that pretty much confirms the diagnosis and you land ASAP with the minimum use of power. In the case of this airliner it is highly likely that the crew either throttled back or shut down the problem engine, did a normal single engine landing and that the post touchdown activities were determined by the evident lack of actual fire (once ATC or emergency crews could observe the nacelle) and indeed the fire warning light may well have gone out at some stage.
JF