But I'm sure competition would then create a better blockchain.

This always remains a technical possibility, but it might not always be a practical one. I think of it like this: network effects are anti-competitive. If bitcoin were as widely-used as the US Dollar, many of its users would be effectively locked in to it and it could take a very large fraud/coercion/censorship problem to actually drive people to a new blockchain.

I'm just saying: competition may not always be quite the solution that many libertarians think it is.