#HaloLore During Halo CE the Covenant board but don't destroy the Pillar of Autumn. In Halo 2, Thel Vadamee is berated for this mistake by the High Prophets.
Perhaps Thel Vadam should have directly ordered the battlecruisers to take care of dismantling the disabled Pillar of Autumn and preventing any UNSC from getting to it by firing some plasma torpedoes at it.