A demigod is a mortal being infused with divine energy. This essence comes from a divine spark in their soul that activates due to some external traumatic event. The demigods ascend to the higher plane to join the true gods in their fight against demons, and occasionally return to the mortal realm for some dire reason, like an invasion.
The religous organization of the world has "chirches" in all corners of the world and operates out of a small city-state, where bodies of great heroes are interred in the maseoleum as a final honor. They are responsible for maintaining the faith and supporting the demigods on earth. On the rare occasion that a demi-god dies on the mortal world, their soul departs to the afterlife. However, their bodies remain, incapable of rotting and staying in prime condition. People would be come together around these locations, sacralizing it. These groups would be similar to the ancient cults of greece. Each dead god would have its own cult of caretakers. They would build a monument to protect the body and guard it day and night.
However, these cults are not affiliated with the main organization in any way, having originally just been from random people who volunteer to come together on this common cause. Rather than collecting the body, the organization allows them to continue. I could see a fee issues with this. The org. Is potentially encouraging a future rival, threatening their power and influence with the people. Branch organizations could sprout from these cults, breaking the faith into sects.
How could the organization allow these cults stay in possession of these bodies instead of maintaining them all themselves?