Souls were delicate for both humans and gods.
To finish transforming Elder Grand's soul, the Goddess of Bumper Harvest had been refurbishing it repeatedly with Divine Power. Though she tried hard to control the power each time to avoid even the slightest backwash and minimize any possible harm to Elder Grand's soul, the refurbishment turned out to be so much that it exceeded the limit.
What was worse, it was the "limit" of the god's part of the soul that had been used up. In other words, since the god's part of the soul had failed in getting through to the injuries, the remaining human's part of the soul had collapsed.
Before that, the elder's soul had been supported by the surrounding transformed parts of the soul like a solid foundation. But once the foundation had broken down and couldn't support anymore, the soul became as fragile as sand sculptures exposed to violent storms and waves. It collapsed in no time.
