Google "price discovery". The amount of people buying, selling, betting on, and betting against a stock (volume and derivatives volume) influence the stock's price. So a hedge fund can look like a hundred thousand regular joes. It's not hidden, secret, subversive influence. It's just a bit subversive.

There's market oversight but it's a joke in some ways. Google "failure to deliver" and "synthetic shares" for some of the latest stuff. There was a way to be sure stock was legit, then there wasn't, then there was, kinda, but we sacrificed that for liquidity (the ability for people with an interest to make an exchange with fewer impediments and less time lag).