Reason being that stock market is a fully regulated one, and it is one you cannot just use large amount to manipulate, which is against the law, so it is easier for you to know which direction stock will go using Fundamental analysis, but if we talk about the most profitable trading, it will definitely be crypto, because it has more volatility than stock market.
One single uptrend in crypto could make you a billionaire over night while that of stock trade can only earn you little interest on your trade at once.