By the word itself day trades, obviously you earn by trading daily or short term even if you get a little amount by it, you can still earn a decent amount if you stake a huge amount of money to buy coins and used it for day trading but it is also the riskiest thing you might do. Day trading became possible due to the high volatility of cryptocurrencies.
Day trading is a term use in trading markets wherein you would be opening and closing a position within a day but since cryptocurrency is a 24/7 market, there is no specific time as to when a market opens and closes so it is up to your time then how would you time yourself in day trading. Some people like day trading because they can scalp some trades and immediately have some profits but the opposite may happen as well like you can quickly incur some losses especially if you are just new to the market and do not have money management.
With a volatile and unpredictable market like today, I think day trading is the best and safest option at the moment. You can see that bitcoin prices are constantly adjusting and causing altcoin to adjust, as the market is in a downtrend in the long-term downtrend so you should trade short-term so that you can preserve interest. when the price of bitcoin suddenly drops.
Holding a coin in a bear market is an eye soar especially when the coin is going down every day that's why some prefer day trading and taking profits from time to time or loss if the market is not in their favor but at least they are preserving their capital. Holding is a good option when you are in a bull market but in bear a market, I think day trading is better but it is more risky too.