I have friends who have made millions from crypto. But every dollar they made is a dollar that someone else paid into the system, that that person is going to lose when the bubble bursts. Enabling that loss is not morally clean.
Is housing not a bubble? Then, how could prices be that inflated in most places, even with a stable (or just slightly increasing) population?
Is stock trading not a bubble, because "real companies exist and have a value"? But, their price is probably 20x their "real worth"?
Is selling vegetables in grocery stores at 20x the price the farmer gets morally clean?
Is it morally clean to keep putting CO2 into the air that everybody breaths?
There are a freaking lot of "unclean" things in the world. I don't understand why a lot of people seem to focus on cryptocurrencies and blockchains.
Similarly I don't see anything wrong working for a betting company or even a company that produce dangerous or addictive drugs.
I consider it morally wrong to work for the government or for criminal organisations which steal money under the threat of violence or kill people for reasons other than self defence.
all of those have so-called market cycles, which is what you described here. the price continues to increase (bull market), as each trader sells higher to another sucker, who wants to sell higher to another sucker... until eventually it runs out of new suckers and the price collapses for some time (bear market). each dollar you gain is a dollar someone else loses. those suckers at the end of the bullrun transfered their money to earlier suckers and lost everything.
the "ponzi" nature of crypto isnt specific to crypto at all - this is how all markets operate.
But when you look at these things from the individual perspective, we all take a risk when buying things. The people that don't assess their risk when they buy lose, the ones that do don't lose.