The main basis for why Stu switched from gin to poker was that he was a tiny bit too skilled at it. So good was he, that no player was able stand up to him. Even the apparently experts who were meant to be the best at gin rummy were blow away when they faced Stu. One such gin professionals was Harry Stein, called, "Yonkie". Harry was handed such a crushing defeat at the hands of mr. ungar that he evidently quit playing it professionally and never resurfaced at a gin rummy tournament.
Of course, with a reputation like that it was not too long before people became afraid of playing against mr. ungar. He could find no games and in his bleakness he started doing something no one had attempted prior. He began offering starting handicaps to likely adversaries with the wish that they might just play against him if they believed they had an edge. He deliberately started from a negative position and one account has it that stu even competed with a regular bad egg. During the contest, he received a few words of wisdom that the bad egg was at it yet again but Stu Ungar assured that he knew of the dishonestly and he would still actually win, which of course, he did.
The same trend followed Stu Ungar into vegas. He won so frequently that the casinos began asking him not to play on their rooms anymore. The explanation why was that other poker room customers refused to sit at the poker table if he were seated.
Stu Ungar is recalled better for his abilities in holdem poker but he always said that he was far more accomplished at gin rummy.
He defeated Doyle Brunson in the World Series of Poker in 1980 to become the youngest world champion. Because of his looks that made him seem far younger than he really was, he got the nickname, "The Kid".