>>719189442
The Prophets completely fucked them over, and worst of all they were lied to. The Rings that the Prophets deemed sacred were discovered to be weapons of mass annihilation. There was obviously a seed of resentment growing within the Sangheili, especially when the Brutes were introduced as their replacements. They pledged themselves to the Covenant so that they could embark on the Great Journey, only to discover that it was all a lie.