Midas had no idea Link was hatching plans at that moment. Neither did he know that Link knew he had an Authority.
If he knew he would have been beyond shocked since he was sure he had hidden it very well, using [Hidden Divinity] to craft a fake Index for himself and deceiving everyone around him about his capabilities and his Skill Descriptions.
Whenever people asked him about his Skills he would merely show them his Fake Index and go about his business. He tried to be natural about things and at other times, when some asked to buy his Skills, he would tell them he wanted to keep them private since they were special to him.
Some people believed him, others complained about it but found themselves unable to change the situation. Midas could care less. As long as he hid his Authority, everything was fine and he would not only not have a target on his back, but also fit in better with everyone.