Well, there are too many factors to consider if a good trader will remain in the trading field. Perhaps they feel comfortable with their stable income through trading. As I can see here the possible reason are, they had a good experience, they had more time to research for any new update, and most of all, they had tools upon giving technical analysis when you execute in trading. Traders that experienced a massive gain will always repeat what they have done but those who experienced losses, will never come back and think of afraid of losing money.
In trading, there could be a winner or loser, not all become a winner, and not all become a loser. Because that is a kind of competition.