Divine Intervention?
After Deus successfully obliterated Haize's discarded body, he saw that Haize was accumulating energy in his body at one point, and with his intelligence, Deus knew that Haize would perform self-destruction.
After all, accumulating energy in one point and holding it in would cause all of the pent-up energy to explode. It wasn't difficult for Deus to guess Haize's intention.
Not only Deus but even Joshua, Jeremy, and Shirley saw Haize's self-destruction. But before they could retreat, the accumulated energy in Haize's body was already released which caused an explosion.
In a split second, Deus used a skill that he had bought in the third system feature before. He had already prepared for such a situation so he had bought a skill that would allow him to react to situations where he needed more time to deal with them.