That's only in a fully deployed system. 70k people won't participate in the first buy of PoS ETH - you'll have a far smaller number, likely less that BTC at scale.

Also, ETH has already forked over a doctrinal issue - I don't doubt it could happen again, but the PoS leaders will just directly double down.

This isn't a PoS/PoW argument - more that most public blockchains are inherently winner take all systems.