Why do the robots believe eating Casshern will heal the world?

I believe the key here is what Casshern is.

Not sure if this is considered a spoiler itself, but Casshern is a robot himself. Or what is known as a Neodroid, or robot with a human mind. He was originally a servant of the robot Boss (Breaking Boss) and was sent, as the most powerful in the robot army, to destroy Luna who was supposed to be humanity's salvation against robot rule.

Casshern went to destroy Luna, but in the process the Earth became toxic. Robots are in a constant state of decay. Except for Casshern, his body is immortal.

So... because Casshern does not deteriorate, and he is a robot, and he is seemingly the cause of the blight, other robots believe integrating him with them will grant them his immortality.