You're conflating the value and price of an asset. E.g. if you own an asset like a stock that pays dividends, the value of that stock is the net present value of the future dividends. The price is determined by buyers and sellers and can diverge widely from the value.

It's related to the distinction between investing and speculating. Investing is based on whether the intrinsic value is below or above the price, while speculating is just based on the price.

Let me rephrase that: it takes a lesser percentage of bitcoin holders vs fiat currency holders selling their assets to collapse the value of their respective currencies.

Or even better: it's nearly impossible to do that with fiat currency, because there are checks and balances in place.

Yes, but all the systems put in place to shield fiat from the booms and busts don't exist in crypto.

For example, the federal reserve and legislators can manipulate the interest rates and the deficit to encourage people to hold or sell their USD.