He followed a very stereotypical Indian religious career. Live as you want to, then get old, then become an ascetic. Ever since India developed cities (which I believe to be the basis of modern civilization), they've wrestled with the ascetic impulse. Jainism follows the Brahmin interpretation of the ascetic impulse.
1) be a kid
2) get married, have lots of kids
3) be wealthy
4) give your wealth to your children and go live naked in the woods
That allows people to do what they want and feel good at the same time. Since Jainism also explicitly allows violence in self-defense or defense of the state... It would have been easy for CG to say "I defend the people by expanding my empire... and by expanding Jian."
It doesn't really matter what religion you follow, spreading it by the sword is pretty much always going to be an option, even when the originator said, "Wait, don't do that". Those who come after will say, "Unless..."