Gao Yang couldn't figure out what exactly the Iron Madonna was planning to do.
Unlike a stable mercenary group like Satan, the Iron Madonna was a typical mercenary group—stable as iron, but its soldiers came and went frequently. The Iron Madonna would never disband, but its members were constantly replaced.
If Satan was left with only Gao Yang, then Satan would be completely finished, gone—even if Gao Yang gathered a new group, it would no longer be Satan.
But even if all the people of the Iron Madonna were dead except for its leader, the Iron Madonna would still exist. As long as there was money, it could easily recruit more members, and the Iron Madonna would soon be fully operational again.