Can you really be sure you will profit unless you have insider info?
This depends on the market you are trading in. Theoretically, in an efficient enough market, trading is 0% luck - buying an undervalued asset would give you a 100% guarantee of profiting. However, the market is not that efficient in real life, and crypto markets are particularly inefficient.
I would argue that trading bitcoin or other crypto is just mostly just guessing, and in some rare cases, slightly educated guessing.
Trading stocks, however, can be fairly reliable and offers just as much or more potential upside than crypto. I've found that every single time I've seen a stock that is under or overvalued based on their fundamental data, they eventually move up or down to their intrinsic value. Sometimes it takes longer than other times, but it always happens. This means that if you buy a stock that you have determined is undervalued based on its fundamental data, you have a very high chance of making money if you are willing to hold it through volatility.
Basically the bottom line is that trading crypto is mostly guessing, or educated guessing at best, and trading stocks is more like risk management, and provides significantly better opportunities to profit.