Now that they had ample energy, the Level 5 powerhouses were no longer that important to the Unknowns. Like the leader said, except for Bella, the other ordinary Level 5 Metahumans did not pose any threat to them at all. So, this was why they did not mind giving Jiang Fei the Core of Life.
However, this was also because the Unknowns thought that Jiang Fei wanted the Core of Life so that he could use it to advance into Level 5, and not to save Bella. Otherwise, no one would agree to hand the Core of Life over to Jiang Fei, including Bennette Straz who had known him for a long time.
In actuality, the organization was not totally unaware of Bella's condition. For example, Demonic Monarch had witnessed how Bella fell into a dangerous situation.