Depending on what your job was (hard / easy, low / high paying), it is hard to say that it is smart or not to quit with it. Regular job is in most cases provides some kind of permanent income on monthly basis, something that you can always rely on. On the other side crypto trading is always risky, one day can be very profitable, and next day you can lost all. There is also a risk of exchange is get hacked, but this is risk every trader must accept.
I would not encourage anyone to quit with his regular job just to go full time in crypto trading, but some people make very nice profit by doing this. I would say that it would be wise to keep regular job with crypto trading, but if after some time someone make good results with trading why shoud he / she would work for some dust.
Probably he knows how much risk he will have to face when choosing crypto instead of current full-time job. Yep, no one can know whether or not he had made a right decision, because in crypto market, we just know exactly the outcome in the end. Personally, with those who resolutely get rid of full-time job to choose crypto are quite risky. If he is proficient in terms of technology, it would be a advantage, he is able to completely earn income for life expenses while he's just working at home.