If one believes Western religious tradition then it wasn’t Man who made that declaration.
I'm thinking Satan. If God can work the pen of man, so can he.
If chapter one of the Holy Bible had "The universe is absolutely gigantic. You are tiny and must kneel in humble awe of God and his creation." it probably would not have been a best seller. They had to hook the reader in early.
For thousands of years man was convinced Earth was the center of the entire universe and the sun revolved around Earth like the moon. The stunning vanity of man knows no bounds.