"#bitcoin's game theory where it's always cheaper to mine honest blocks for rewards instead of 51% attack, only works with rational thinkers...As millions of dollars have been burnt fighting between two forks of a fork of bitcoin have shown. Crazy breaks the checks and balances."
Don't get short term incentives mixed up with long term incentives.
In other words, bitcoin has so much hashing power thrown at it, that it takes way more money to attack it than to play fairly.
Surely, there could be another test of bitcoin in terms of billions of dollars thrown at a hashing war, but let us see how long such a war would be sustained, if it were to occur, when the users are not going to accept or recognize such.
Similar threats were made in 2017 regarding assertions that mining power rules the bitcoin world, and it seems those assertions were shown to be untrue in actual practice... even if you believe miners are going to gang up or get sufficient mining power to sustain a 51% attack, even for several months, and they threaten to do it, we have to see whether the rubber will actually hit the road and they will do it, and we will have to see if bitcoin users go over to that take over chain.
The thing is those theories only apply in a certain set of circumstances. For example, it was never intended to apply to minority forks or altcoins using an algo in which Bitcoin is king. All those are completely vulnerable to a 51% attack. They shouldn't even exist but were artificially allowed to because of.... reasons.
51% attacking Bitcoin? Well, you couldn't rent enough hash to do it so it would need to be done by the very same miners that make a living out of it. And yes, for those the rule that attacking it instead of honestly working on it clearly applies.
Current Bcash shenanigans do not contradict, but in fact confirm the theories..... and they haven't even really started attacking each other yet.