Not an expert, but: if there had still been fuel supplied to that engine, the fire would have been a lot worse. If you watch the video the fire clearly becomes less intense over time, and the footage of the landing suggests it's out by then. Remember that fuel isn't the only flammable thing there - engines need oil for lubrication, and in combination with whatever residual fuel was in the system and potentially sprayed everywhere, it's not surprising that you'd have enough to burn for a short time.