Decimus was once a zookeeper that took wonderful care of all the animals (rahi) in the zoo. Then he heard of matoran and biomechanical life not treating the environment the way they should. He then found a to stone and went out looking for toxic villains that he could send into deep orbit in order to stop pollution.
This story is inaccurate seeing that the bionicles would never harm their planet. It's just a story I came up with.
Actually they would try to harm the planet, for energized protodermis, if you read the Canon story.Spherus magma Blew to pieces when the energized protodermis was all remove from the core, which made it into 3 planets.