There is no such thing as speculation by mining - if they wanted to speculate but didn't profit from the mining itself, it would be better for them to speculate by buying - instead of giving dollars to the power company, they'd just give them to other people on the exchange. Basically the only reasons for miners to "speculate" are long term contracts like lease contracts for warehouses. And those may or may not be long term.
And 51% attack has the designed side effect that all other people stop using the currency - they may keep following the previous fork without the double-spend - as shown by ETH and ETC. You'd also need some way of forcing all participant to stay with the now corrupted currency. Otherwise the attacker who performs 51% attack will gain the ownership of a network that immediately becomes completely worthless.
> And 51% attack has the designed side effect that all other people stop using the currency
That’s my point. That is literally the point. That is why it is a bad thing and why no sane nation would ever allow it to become their main currency. It is an attack surface. It is a vulnerability to your economy.
And 51% attack has the designed side effect that all other people stop using the currency - they may keep following the previous fork without the double-spend - as shown by ETH and ETC. You'd also need some way of forcing all participant to stay with the now corrupted currency. Otherwise the attacker who performs 51% attack will gain the ownership of a network that immediately becomes completely worthless.