You actually have an incentive to collude and carefully manage the market, then crash it and buy all the money back and go back to hoarding it.
With sufficient deflation, you end up spending less on necessities (food) then the rate of increase in the value of your horde. Making you the permanent upper class, and making everyone else the permanent lower class. It's a return to feudalism.
In traiditional currency systems the central back adds more money to the supply by buying financial products
In your scenario the 99 people add currency to the money supply by buying whatever they opt to buy.
The differences are that the central backs can print as much currency as they want rather than being limited to what they bought earlier and that it's many people vs one institution with some mandate to keep the currency and economy stable.
That said, if I was one of those 99 I would be careful and probably collude with the other 98, if I tried to cash out too fast I would collapse the value of bitcoin and the rest of my investment would be rendered valueless. So they do have an implicit motivation to preserve stability.