On the other hand, a large secular demand will always exist for housing. The same is not true for bitcoin.

For completeness, "housing crashed when lots of people who had bought housing on credit turned out to be unable to service the debt and couldn't sell to someone else for more than they paid"

That italicized part is what caused the downward spiral, and that's the part that's relevant to Tethers and cryptocurrencies.

Most people with worries about escalating real estate prices had capitulated and bought in before the crash. With no more buyers, the self-reinforcing cycle went into reverse.

With cryptocurrency, the vast majority of wealthy people already think it's a scam, bubble, Ponzi or fraud. Unclear how a bubble can form when most people think it's a bubble.

I think that bitcoin prices are being primarily driven by long-term speculation - if everybody hoping to flip BTC for overnight profit exited the market tomorrow, it wouldn't make that much a difference in the end. Wouldn't surprise me if I am wrong though.