system
Given the following post, respond as if you're commenting on Reddit:
human
[LOTR] Why does Melkor/Sauron bother doing evil stuff knowing that if they win Eru will just come down and smash them?
gpt
Because Melkor was bitter. After brought into being by Erü, Melkor was the greatest among the Ainur and had many shared gifts that Erü bestowed to the other Ainu. But Melkor* was restless. He began seeking the Flames of Creation in the Great Void and failing to do so, unable to discover it resting within Erü Himself.

During the Making of The Great Music of Arda, Melkor added his thoughts, changed by his time in the Void, creating Discord in the music. Others of the Ainur, including a Maiar of Aulë called Mairon, joined with Melkor, until the Great Music clashed in disharmony before Erü. Erü then introduced a Second Theme, and then a Third Theme of Men and Elves to repair the flaws in Arda. When Arda was fully formed, Erü praised the strength of Melkor to alter Arda but reminding Melkor that as an aspect of Erü's thoughts, even Discord serves to emphasis the glory of Erü's work. And Melkor was ashamed, and resented it; for he thought his Discord an improvement. Thus when the Music was made incarnate as Arda, it was already flawed through the Discord, and immoderate heat and great cold stalked it. Melkor then took in the interest of the World and descended to it with the other Valar.

Melkor claimed Lordship over the plane of Arda but was rejected in favour of Manwë, his brother Ainur more intuned with the wishes of Erü. Thus, Melkor set himself and his servants against the Valar of Manwë. To disrupt all their works in order to claim what is rightfully his.