Only until he saw the text prompt did Leon realize why he got the Golden Finger reward without doing anything special. All he did was catch a camel, throw it into the Molten Lava Lake to roast and eat, and suddenly he received the reward.
Indeed, he hadn't done anything recently, but that didn't mean he hadn't done anything before. A year ago, he had arranged for the Efreeti to transform the Steam Lake, and now that the Steam Lake had become the Molten Lava Lake, the inspection was successful. You reap what you sow, and it was time to harvest.
At the same time, the high-level reward was something Leon had not anticipated, but upon further thought, he could understand.
Normally, to change the environment near a lair, it would require an Adult Dragon, or at the very least a young dragon with exceptional talent. But he didn't have that ability; it was all due to subduing the Efreeti, who had a natural talent for environmental transformation.