but over 75% of nodes and the economic consensus decides not to which would be very dangerous
No its not - if they choose to follow anything other than the longest, valid chain then they are no longer following bitcoin. If they want their coins, however, they will.
most of the economic will simply do nothing tho, they will have stake in both forks, and watch as one of the forks loses all its value.
so in a way speculators are the deciders.
Indeed, but as it will only trigger @75%, the tipping point will have been reached and the majority of undecided nodes are unlikely to remain on the lower hashrate chain.