I think the bull run is not purely speculative on nature, of course speculators make money during the bull market but it is definitely not the way it starts. One day something big happens, sometimes not even anything big needs to happen and than the price starts to go up, one day it goes up like %10 than it goes up another 7% than when you look at the whole week the price increased like 50% or more and than it keeps happening like that for a month and increases like 300% or whatever total.

Speculators do not have enough power to neither keep it low or stop it so what they do is just get in and try to pay their way into the bandwagon and keep the price going for another while until they get out with their money. Sometimes when they leave it makes the market crash because the price already stays on thin ice after a while but sometimes it just keeps going.