The immortals were born as the dark one's sidekicks; however, they had turned the tables around and become equals of their masters. Patroclus' intention was clear: he would conquer the human world first, and transform as many humans into immortals as possible. By then, he would be regarded as the god by both the Zergs and the humans, making the immortals a master race of both.
The humans still fighting against Patroclus were born in the old human world and had the old mindset. As Patroclus would bring the war to an end, he could easily remold the humans' mind using religion and make his subjects worship him like a god and savior. While the humans could achieve immortality by binding themselves with a Zerg, the Zergs could also gain what they wanted for centuries: a soul.
It was a match made in heaven.
