As long as they are not greedy for profit, they can profit from bitcoin trading. The bitcoin market is still going up and down erratically and will continue to do so. People who already bought it at a low price can now sell it for profit but can also hold it for longer and only sell it when the price rises higher than it is now. Getting 20%-30% profit is enough because it is very difficult to make a profit nowadays.
The quick recovery is basically just the proof that we are in a market where 20k is pretty strong resistance. People know that it was the previous ATH in 2017 and they believe that we are not "that" bad right now and that is why buying when it is under there is pretty easy decision.
Doesn't mean that it can't go lower, it can still go lower way down if people end up selling a lot, but there is a difference between 40k and then suddenly under 20k, it is easier to buy some here. I didn't do it unfortunately, I should have done it, considered doing it but honestly I didn't had the courage this time around because felt like maybe it would go down more, it was a mistake, wish I bought some more.