Hashpower doesn't matter. Miners follow price which follows economic demand. Mining is at the very end of the chain of causality, not at the beginning or middle of it.

The failure of the Segwit2X fork exemplifies this perfectly. If hashpower truly were as important if you say it were, then Segwit2X wouldn't gone ahead with >90% hashpower support (software bugs notwithstanding). Instead, it was called off for lack of consensus within the community, and the miners stuck around afterwards anyway. That 90% figure isn't nearly as important as you're making it out to be.