Melkor at the time when the Valar only took the form of the Eldar. According to my ideas, they did not have a very clear idea at that time about what would not shock the elves and would not embarrass them. And they also had a vague idea about clothes. Well, Melkor also liked to attract attention in principle. And yes, crowns. The Valar, according to my ideas, again, at that time had such crowns as a manifestation of their power, and the Eldar, in their likeness, then began to make metal crowns for themselves.