Could large financial institutions pump up BTC just by buying a lot of it?

Since the price of BTC is entirely derived from speculation couldn't a company like BlackRock buy large amounts of BTC which would drastically raise the price, this would then cause an upward price cascade because more and more people would pour their money into BTC because they don't want to miss out on the rally. BlackRock could then sell their BTC into the demand that they created by buying those BTC.