Why Does Good Suck So Much?

[Galadriel55]

Morgoth wsn't created to be the "base drum" of the ainulindale that covers all other sounds. He chose to do so. In the beginning, he wasn't evil.

Yes, Sauron helped destroy Numenor. However, the Numenorians chose to listen to him and follow his instructions. Moreover, all Sauron did was speed up the decline. He wouldn't have been able to do so if there wasn't a good fertils soil to plant on.

Some of the major virtues in the legendarium are pity and forgiveness. Those who do not understand them...

Originally Posted by The Voyage of Earendil and the War of Wrath

He thought that he forever estranged the Noldor from the Lords of the West, and that content in their blissful realm the Valar would heed no more his kingdom in the world without; for to him that is pitiless the deeds of pity are strange ad beyond reconing.

And look what happened to Morgoth!

We see many characters achieve certain wisdom through forgiveness/pity. Bilbo, Frodo, Faramir, Turin to some extent, etc. Eonwe forgave Sauron when he surrendered. Just like the other beings in Arda, he couldn't predict what this would cause.