Daily more people are getting rich through bitcoin and other cryptocurrencies. It can be through trading, gambling, mining or various other services and in specific holding. Users who invested at least $10000 - $15000 by January month of ongoing year probably could have turned rich if he's in a third world country.
Your title says one thing and your main post says some other thing. You are only thinking about the people who are getting rich through bitcoin and other crypto currencies, but what about the people who are losing shit tons of money while investing on crypto currencies? And gambling is just a way of getting rich by carrying a huge risk over your shoulder. The price of bitcoin was just around $4,000 USD in January this month. They just doubled their investment, doesn't mean they became rich overnight.