Robinhood Markets has joined the S&P 500 Index as of September 22, becoming its best-performing stock year-to-date with a 229.2% increase. This surge is attributed to strong financial results, user growth, and the company's expansion into various financial services, including new products and a community for traders. However, questions remain about whether Robinhood can sustain its momentum amidst its evolving business model.

Robinhood exceeded earnings expectations by $81 million, adding 2.3 million new users and achieving 45% year-over-year revenue growth. With significant increases across various metrics and a diversified business model, the company is better positioned for future market fluctuations compared to its previous downturns.