It’s not a group. Each of them deciding individually. If a miner wants to a back a fork with a shit ton of KWh, then they’re free to do it. But since they’re producing that energy themselves, they know it doesn’t grow on trees, and they’ll count to 10 before spending it on the newest fork.
Up to each miner to do economic calculations for the upside of supporting a fork. And looking at all precedents, there isn’t any.