Even crypto trading is can gain so much money in some quick time, don't forget that crypto can also lose so much money. And note that not all people can trading.
And I don't think trading can be main job (maybe there is anyone do that but still, they need a job to make money to be traded) And if a country only depends on trading, I can say that the economic would be destroyed and maybe the country would be bankrupt if crypto price down to the floor
Sure, no nation will solely depend on trading as main source of income; this is solely for the citizen that wishes to have something doing to earn a living rather than stay without a job.
It is better to have something doing that can bring income no matter how little than not to have at all which trading will definitely sort out. Trading actually can be done by everyone with interest, to me, I believe everyone can actually trade; all that is required is the right knowledge, mentor and little capital.
In my country, I see where lots of highly educated people complain about not having job but yet, they buy airtime for as high as 5 dollars on their phones virtually every day, do you know we have people that trades with 5 usd and grow it ? So, trading can actually be solution to lots of joblessness out there.