The purchasing power of 1Us dollar vs 1Bitcoin clearly shows that one is going to zero, while the other is not.
When we compare Bitcoin with the best, most used fiat and most reliable currency in the world, the Us dollar it clear show that Bitcoin is on a different level to the Us dollar.
Let me show you why wealthy men like changpeng Zhao(cz), Brian Armstrong, Jed mc Caleb etc can hold billions in Bitcoin without being afraid.
This people you just mentioned are not just investing in Bitcoin because they have the money to invest, these are men that truly understand bitcoin and are very sure of what they can gain from bitcoin. Have seen people who can afford to buy bitcoin but they didn't last long in the market because they do not understand the market.
Investing in Bitcoin can work when their is understanding to know what the market is all about, then invest accordingly to what you can afford to lose. Investing in Bitcoin is not about being rich but having Understanding , understanding keeps one calm knowing that their will be a time to make profit.