I mean, it was up to the community at large to ultimately support the new fork. As an example, Bitcoin forked into Bitcoin Cash, but the community largely stuck with the main chain. It's really a market-driven decision which chains or forks thrive and which ones don't. At any rate, it's more and more expensive to do forks as a chain grows in maturity and adoption.
Sure, but do you think "the community at large" really makes such decisions in any meaningful way? Overwhelmingly, "the community" blindly follows a few leaders who happen to have a high profile or make the most noise in the right forums.
Which means that in practice, these "immutable" blockchains and their "code-is-law" contracts are immutable for the masses, but can be modified (in effect, by forking) when it's in the interest of a few powerful individuals/entities to do so.
