As soon as Ji Mengyao and the three young masters escaped, the 1000 Noble Lord Realm warriors descended into chaos. They were not actually warriors from the Serenity Plains. They were allocated here by forces of Central Plains off the record and they didn't belong to the Hades Society or the Samsara Palace.
The formation was not constructed within a day or two. It would require the warriors to learn to cooperate. After all, if one among the 1000 stood the wrong position, the formation would fall apart.
To make today's plan work, Ji Mengyao had taken great pains. She put in a lot of effort just to recruit the 1288 warriors. She couldn't have used warriors from the Samsara Palace or the Hades Society or else the Demon-slaying Hall could hold the fact against her. She could only buy off some warriors secretly or use carrot or stick strategy on some warriors.