Miners are the arbiters of consensus because they extend the blockchain. They are the group who's interests are most closely aligned with the success of bitcoin. They are the only people with a commitment. Hodlers can dump whenever they lose faith. Miners have to fight to preserve their investment. If they do not do what is best for bitcoin, they lose BIG. Who do you want in charge, fickle hodlers who can jump ship to a different coin if they screw this one up, or miners who have huge amounts of capital invested in hardware that is useless without bitcoin? Every governance system in the world is minority rule. Pure democracy is 2 wolves and a sheep deciding what to have for dinner and nobody is dumb enough to use it as a governance model for anything of value. It would be even dumber to cast votes based on who has the most money.
Miners can not unilaterally change consensus rules. Well they can try but that's called a 51% attack which is what Satoshi warned us about. The economic majority also can not unilaterally change consensus rules by the way, it requires the support from the entire community. This is what makes Bitcoin resistant to change and thus also attacks to force through changes that benefit certain groups. Giving miners all the power to change things would be incredibly stupid, especially when mining is centralized like it is now. I don't want to trust miners to do the right thing for us all, Bitcoin was invented so it wouldn't require trusting humans to do the right thing.