Because Melkor Sees It As Him Showing Off That He Has The Best Gossip And One Uping Manwe - Tumblr Posts

the one trait Manwe and Melkor have in common is that they are massive gossips. the only time they get along is when they're telling each other the latest rumours they've heard. Manwe snuck into mandos to gossip with melkor during his imprisonment and Melkor regularly gives captive elves gossip to tell namo when he kills them so that he'll tell manwe. Manwe never thinks to use this to help the elves in the war against Melkor