The thing that defines it to be a Nash equilibrium: namely, a Nash equilibrium is such, that for any individual entity, deviating from the strategy that consists of the Nash equilibrium is less advantageous than keeping with it. So once a system is in a Nash equilibrium, no individual entity has any incentive to leave it if it acts alone without collusion.
A Nash Equilibruim suggests there are different strategy profiles. In the context you present there are only ONE set of players, the miners.
Yes, you are right, the system is more complex, and there are also the users (people buying and selling coins essentially). But the Nash equilibrium is essentially this one, where the miners can only stick to the original protocol
Why? Who evaluates that they have done so?
Of course, this equilibrium can be broken, which is exactly the case of "forking away" and hoping for success in the market, but it needs a form of collusion between certain miners, and enough users.
As I said many times, this is a NATURAL way of evolving crypto: forking away, taking the risk in the market. With a PoW coin, this has to be initiated by miners.
Yeah? Watch UASF
Economic actors do technical analysis on coinmarketcap, or use any other betting strategy. The debasement is never part of these considerations apart psychologically maybe. The market price includes already all debasement
How does the market come to learn about debasement?