Then he started worshipping Astrotrain. You can see where it went from there.
The Transformers cartoon
Jero was a High Priest of the Titan Sky God, whose statue Jero could control. He used his people's beliefs to enslave them, forcing them to offer sacrifices (food, mostly) to appease the god. Then Talaria led a rebellion, and captured Jero. She tried to convince the people that there were no gods. Unfortunately, Cosmos crash landed right in the middle of her insurrection. Then Astrotrain arrived, and convinced the Titans that he was a god. Jero was immediately acclaimed high priest of Astrotrain.
He basically became the overseer of the mine where energy crystals were to be given to the Decepticons, and later tried to sacrifice Talaria for helping the Autobots Jazz and Perceptor. However, Omega Supreme crashed the sacrifice. Knowing that they couldn't defeat Omega, Astrotrain decided to destroy the crystals. Jero was left to "die like the worm you are". He was not seen among the Titans who survived, so he may have actually been the first person to die in this particular section of the multiverse.
- Jero's face strangely resembles Scourge.