Silly question here, why were the account books buried instead of burned? Do the books have any use in future if they never got caught?
If you just base you ponzi scheme on I take 50% of every new payment and give out the previous 50% to my previous investments it won't really drag on for longer than couple of months, not to mention that you actually need to generate allot of financial traffic to both draw people in initially and keep the authorities of your back.
The reason ponzi schemes tend to snowball like this is because they run exceptionally well many of them have actually made some decent return on their investments (not anywhere near the actual percentage needed to balance out the "management costs" ofc) a good ponzi scheme is almost indistinguishable from a legitimate investment fund, they'll make tons of trades, constantly move money around and keep large cash flows on hand to make it look like all the money is still there, make regular payouts, and "silence" any panicked investor who wants to cash out early.
Regulators probe the market constantly if your trades don't add up at all you'll get caught in a minute lasting years and managing to steal 100's of millions or even billions of dollars doesn't seem something anyone could just pull off, I think you underestimate the intelligence and skills required to run these sort of scams.