When the plane collapsed, all the people and things turned into fragments by the distorted space.
Flesh and earth mixed together, and a power from the Underworld pulled at that world.
There hasn't been a plane that had such an abnormal fall for a long time.
In general, even if a Secondary Plane's lifespan was exhausted, at that time, there would be Gods specialized in presiding over the world's judgement and destruction.
And an event like the battle between the Crypt Monster and Glynos, destroying the plane in the process, hadn't happened in more than a millenium.
Everyone could feel that the order of the Universe was getting out of control, step by step.
In the God Realms, those Gods who had been laughing at the Black Dragon God also began to worry about whether their Secondary Planes would be attacked by unknown enemies.