Easy to understand
1. I have to work (mine) therefore the item should have some value more then the effort I have put in.
2. As I have decided in my own mind it has value then is the value I assign to it higher or lower then other peoples value.
3. I can always find a sucker who values mine for more then I do, I should sell mine to him/her.
4. That sucker can almost certainly find another sucker to sell them to for a higher price.
5. Hey! There's a market....I should mine some more and sell them.
6. Rinse and repeat.
I find it amusing that people argue the underlying value of cryptos is worthless (a notional concept) while at the same time buying banking shares which have proved historically to be worthless time and again when confidence evaporates.
Any system, except direct bartering is smoke and mirrors to some extent.