First off, George Soros had been a pretty successful hedge-fund manager with his QUANTUM FUND back in the late 80's before he made a bundle on the devaluation of the British Pound.
In fact, he was so successful making "macro" bets that he charged a then undheard of management fee of 4%!!!
As for his British Pound "trade" . . .
It was a total "lay-up" because the British economy was already in a recession and trying to keep the pound strong with interest rates as high as they were was plain insanity. Had the British not allowed the pound to "devalue" the entire county would have gone into a DEPRESSION. Hence, Soros leveraged up a position that was very low risk and textbook Econ 101A.
As for George Soros himself as a trader, he too has his faults and "mistakes" just like the rest of us. Just take a look at the Crash of 1987 and how he tried so "naively" to unload over 5,000 S&P Futures on the opening on the Thursday after Black Monday. . . He got nervous about how the dollar was trading overseas on Wednesday night and decided to unload his S&P futures position ( his fund was exempt from position limits ) and he had no idea that the markets were "thin" and that the locals would never stand in front of a "freight-train".
Instead, they "front-ran" his 5,000 lot sell order into OBLIVION and the S&P traded all the way down to an incredible 45 point discount and a "print" low that was insanely out-of-whack" with the cash markets. His sell order MARKED THE DEAD ASS LOW.
So much for having a mechanical "working" knowledge of the financial markets.