In this case, Fëanor’s paranoia around the Silmarils
is justified. Melkor wants the jewels and will do anything to get them. This, too, contributes to Fëanor’s certainty that others like the Valar and his brothers are attempting to steal what is rightfully his. The Valar recognize the threat that Melkor poses to Valinor and the harm that he’s already done—Valinor’s age of peace has ended, and the world is sliding into conflict again.