As you say, fortunes were made.
Suppose a politician announced a policy they have no intention of implementing. The goal is to affect a stock price. Trades are made and profit taken.
Then the politician reverses the announcement but has pocketed a fortune.
When somebody wins big on the markets, that monetary value comes from somewhere. For everybody who made a fortune last week there will be lots of others who lost their shirts.
Yeah but small fortunes were made in shorting the pound so still trebles all round