In a standard 'pump-and-dump' scheme, the ‘dumpers’ hype up demand before aggressively selling their bags into the built-up demand. During the dumping, often called a rug pull, usual market dynamics apply. Eventually, the supply offered by the dumpers seeking to squeeze out every penny dominates demand, and the price crashes – pump-and-dump completed.
The nature of the pump-and-dump scheme is such that profits are created while killing the token in the rugpull. The success of the pump-and-dump is determined by how much exit liquidity you are able to make.
Whether intentional or not, the Terra dollar (UST) worked as the perfect exit liquidity in what can be described as a prolonged pump and dump scheme. A combination of Luna supply control, the psychology of the dollar, and guaranteeing high yields secured with their own pre-mined tokens created sustained exit liquidity.