When the crash comes I think crypto is going to fall with it, people will sell assets to pay their mortgage bill regardless of type. However I think once it has settled, once big money starts buying up assets cheap, crypto is going to be one of them!
People do not pay their mortgages "no matter what", in 2008 there was tens of thousands of people who got kicked out of their houses, but when a crisis comes and the financial world collapses even if the banks seize all of the houses at the first sign, they still have to sell them and they usually sell them for far cheaper which means they will have to both wait and also not make all of the money back.
It is really not an easy task and proof that people sometimes do not pay their mortgages, so they may not sell their bitcoins if it is not even remotely close to their mortgage. Sure if they have to have their cars repaired or something they might sell but a guy who has 100k mortgage debt do not have 100k worth bitcoins, they either have zero because they are in debt or they have a very tiny amount.