But does anyone control it?
Ask yourself this—
How are Bitcoins created?
Who is incentivised to create Bitcoin?
Between 2013 and the beginning of 2017, big money had been slowly moving in on Bitcoin. They saw its potential as a relatively rare asset and also the mechanism that made it work. Bitcoin is seen as having a value greater than the sum of its parts.
Bitcoin is not a market, it is a single asset. You need another asset to indicate a trade and hence a market. If your other asset is the USD, then of course the USD issuers can have the largest control of this market, being able to take as many bitcoins as they like at any time, in the time honored method of fiat practitioners since Kublai Khan. Other than that, every participant in a market has some control, some via influence to market logistics, others via their influence with market makers, others via their control of some of the assets themselves.