It comes down to their trading skill some are good at day trading or short term trades, so we couldn't really say that they could never achieve anything big.
What if they are making use of the Bitcoin price movement on short term trades to gain more Bitcoin rather than just holding their Bitcoin?
We should never look down on those short term investor, they could always reinvest their winnings to gain more.
Many of them don't reinvest their gains, they spend it on looking rich and they miss to buy Bitcoin before it starts pumping again. Investors that do short time investing don't make profits like investors that hodl for very long. They can decide to sell Bitcoin in profits but the profits don't get reinvest and then the won't own any Bitcoin while Bitcoin is pumping. If you're trading frequently you can make profits but also you can lose too if you don't know how to trade very well. Investing in Bitcoin for long time will make you to not be worried and you can do other things to bring more money so you can use them for buying more Bitcoin. Being in the market regularly will make you to have a short time mentality for investing and it'll make you miss out of bigger profits opportunities.