Peter Brown, knowing his crisis, developed an idea: before the Higher-Ups took action, he would strive to secure as many rewards for himself as possible.
After the departure of All Saints, Peter sat cross-legged, pondering deeply. It became clear that the Saint of Heaven Origin couldn't deceive him; this crisis was likely imminent. The Giant Beings were strong because they likely had powerful backing, and even if their backers wanted to act against him, it wouldn't be easy now with the Giant Beings just wiped out, giving him some time.
Understanding his situation, Peter knew his key card was the Killing Saints Formation; possessing it gave him the power to resist at any time. Hence, further upgrading the power of the Killing Saints Formation was crucial for him.