O His audience, Christ's claims must surely have sounded sensational & grandiose. He claimed to be God. The word "cosmic" is far too small for the kind of assertions that Jesus made about Himself. Matthew 7:21-23 alone reveal that Jesus was declaring not only that He was divine, but that He was the ultimate Judge of all men. This was quite a statement, especially coming from a mere carpenter from the northern outskirts of Israel. Something needed to be done to verify Jesus' presentation of Himself. Matthew 8 serves (in part) to validate Christ's identity as the eternal Son of God who was simply robed in human flesh. Here we read of Christ healing a leper, healing a servant with the palsy, healing Peter's mother-in-law, calming a storm & removing evil spirits from the Gergesene demoniac. In addition to the many fulfillments of Old Testament prophecies, the raw power of God (that flowed from Christ) shouted His identity loudly.
Now, in this chapter there are two events that are presented without Christ's comments. Of course, these still validate Christ's claims. Mathew 8:14-17 do not include red letters, but Jesus was fulfilling prophecies by healing the infirm. And, here Matthew doesn't include Christ's words in Gergesa, but the power that Jesus had over the devils there was enough to communicate the point sufficiently. This man, Jesus of Nazareth, was not just a good man, nor was He even just an exceptional man. He was the God-man.