More likely, Hillary’s success was backdated trades.
The trades were recorded much later, when the broker knew the which way the market had already gone.
If so, it was a payoff to Hillary and/or Bill. But, by who? Probably not the broker, but they could have booked backdated losing trades for someone else and balanced their books.
You sound as if you understand money. It’s useful to know the different ways one can invest, even with a middle to low income.