The once low volume that caused a bit of a spike suddenly changes to big volume. The stock manipulators sell out their positions into the new buying brought on by the promotion campaign. No more news or insider leaks of information to pump the stock to get buyers. The front loading sells out. The silence plays on the emotional fear of being hoodwinked.
Negative opinions begin to spread across the financial world.
Joe public sells out to cut their losses. The really slick market manipulators would even seed the Internet news groups or other journalists to plant negative stories about that company. Or start a propaganda campaign of negative rumors on all available communication vessels. As the Shorters were shorting the first manipulator was selling, so now it goes the other way. Buying to put pressure on the shorter to cover.