Or rather the majority of actual users. Hard forks occur because people install and use the updated clients. If 90% of the miners decide to mine on the “bad” chain, but 90% of users switch to the “good” one instead, the “good” would likely still win out in terms of market cap and recognition (and the miners would naturally have to follow).
The odd part is, the governance model is not defined. At the end of the day, some person or group has to decide what the new "real" Bitcoin is and the average holder just has to go along with it.
The opposite is also true – most miners have stayed on the “official” chain :-) I do agree that having more hashpower helps, but ultimately all users (including miners) determine the price on the market.