What Happened to Genesis?

If Genesis from "Star Trek II" and "Star Trek III" was a failure because of the use of the unstable material protomatter in its matrix (a fact only speculated on by David Marcus who was unable to do any research since he was killed afterwards) then how did the Genesis cave on Regula survive intact for almost a year according to the video recording made by Carol Marcus?

It is possible that protomatter was not infact the problem, but rather one of the following explanations:
  1. Khan's followers, not knowing how to properly operate the device, did not program it correctly.
  2. A material in the nebula interacted unfavorably with the Genesis wave effect thus making it unstable.
  3. The Regula planetoid was not suitable for a full-scale test of the device if that is your preferred source of the Genesis Planet (I personally believe Regula was the Genesis Planet, but others think it was created directly from the nebula which is a little too advanced for my tastes, even in comparison to the Genesis torpedoes alreay amazing capabilities).
  4. The nebula was not a suitable source of material for creating a new planet out of nothing if that is your preferred method for creation of the Genesis Planet.
(Theory by Bond, James Bond)