We will believe that some good outcome will happen anyway explainable away by the almighty being doing the heavy lifting. Because not even us know how exactly the outcome will happen, quite often, no body can sabotage it.
Because others see what we believe, others may believe too. After all we have so many arguments in the world. What is more convincing than to see someone, out of his selfish interest, believing the same thing?
When people believe something, they bet on it. Say you believe that Yuan will go up, you too will long Yuan and short USD right?