After all, how much would it cost to manipulate the BTC/FIAT exchange rate ? after all - there is a very limited number of exchanges, and trading volume is not as high as is the case in the traditional Foreign exchange
The gold market was being manipulated at the total value of the gold in the world is 7 trillion USD.
Bitcoin has a market size about 0.04% of gold's, so is easily manipulated. It is also more fungibile and has fewer exchanges, so can more easily be manipulated.
I personally don't think there is any genius plan to keep the price high/low, just inpatient people following trends.