The siege weapons were slow so they couldn't avoid getting hit. The soldiers who were guarding the siege weapons prepared defensive skills to block the meteor but one of Jack's clones that were nearby commanded them to leave those siege weapons. He saw who cast the spell and he knew those soldiers wouldn't be able to do shit against the incoming meteor.
It would be a great loss to lose those siege weapons but they had already made a hole in the wall. Losing the siege weapons would just be a financial loss. He didn't want the soldiers guarding the siege weapons to lose their lives as well.
The meteor landed and obliterated all the siege weapons within the impact zone. Different from the normal Meteor Fall, the chaos version caused a shockwave that radiated outward. This shockwave dealt chaos damage to those it passed through. Low-level and low-grade soldiers who were still fleeing from the impact zone were killed upon contact. The rest lost a large number of HP.