If each sentient being had free will, then each sentient being would require its own law. So that means we're positing billions, trillions, zillions of extra laws - one for each sentient being that ever has existed or will exist. Do you understand why that's what free will implies?

But that's why it violates Occam's Razor. Because we're basically positing unlimited unique laws, instead of just one.

Nothing about how sentient beings act requires us to posit more than one will. That'd be akin to suggesting that different computers running different software must be demonstrating totally different laws of nature, just because they're behaving differently. But no, computers everywhere are always just demonstrating the same laws of electromagnetism, etc. And humans are the same way.

Also, the model I'm positing here has nothing to do with humanity's tendency to fall into a herd mentality. To explain group dynamics, I'd look at Game Theory.