How the Pumper and Dumper make money?

Hi together,

first sorry for my bad English, but i never had it in school and must learn it alone.
Quiet for that situation i think it is good enough to understand :-)

My Question and also my first Post is the Question how the Pumper and Dumper make money?

For example yesterday their was a big P&D in the Foldingcoin (FLDC) on Poloniex.
I know the Pumper buy first and got a good Price. But where from the Pumper knows the Peak of the Price
to sell. And also it is possible that nobody buys at the Peak. For me it is very Risk and i dont really understand how
people are able to make money with Pump and Dump.