People are free to disagree with and act against the developers. That's more than you can say for, for example, the United States Government; if I disagree with tax policy or federal monetary policy, I (may) have the option to leave, but changing the system would take a lifetime, if its even possible. Creating a new system without moving countries would inevitably end with the police at my doorstep.
Miners want money. Ethereum, like every currency, is worth what it is because of people. The value of Ethereum goes where the money velocity goes; in other words, where the users go. The critical question is not what the developers or miners support; its what the users support. Well, barring any major conflicts of interest, they'll/we'll probably support the developers; their power comes directly and only from the trust that the collective democracy of ethereum's users has in them. If Vitalik demonstrated extreme prejudice against ethereum's users, then the users would (probably) revolt, and new developers would be installed, but critically: Ethereum, like all blockchains, enables that in a way which doesn't involve the war, death, and bloodshed that overthrowing governments typically requires.
Miners want to have their cake and eat it too. They don't give a shit about Ethereum's users. They want a high ETH token price, wholly and totally supported by Ethereum's users, but without this RFC, which both the developers and most users support. They could fork, give the middle finger to the users, and their secondary TRASH-ETH blockchain would be worth nothing, because it doesn't have users, but at least they'd have proof of work. That's why they'll lose; not because the developers are on the other side, but because the users have put their faith in the developers, not the miners. And that's a very healthy position for ethereum to be in right now.