I don't believe all cryptos are a Ponzi scheme. I don't feel that way about Ethereum or Bitcoin for example.
Anyways, you shouldn't be so concerned about how to 'crash crypto'. Many crypto currencies have crashed multiple times over their lifetimes. BTC alone recently crashed 30% or more (as it did several times in the past). There will likely be a future crypto crash related to Tether.
There are definitely lots of crypto projects that are complete BS.
But the concept of cryptocurrency as a store of value of medium of exchange does indeed work and is no different from fiat currencies.
Whether cryptos are overvalued at the moment is a different question, but it doesn't mean the concept of cryptocurrencies are BS and should be shut down.
The entire crypto market is a house of cards built on the fiction that "stable coins" are actually backed by something financially "stable". An unsecured "loan" does not meet this definition.
More than half of all crypto trades involve stable coins so this is the foundation of the entire crypto marketplace.
Give it to bankers :-P