El Salvador abandons Bitcoin as legal tender

But that doesn't distinguish Bitcoin from other cryptocurrencies. The thing that distinguishes Bitcoin is fame, pure and simple. Everyone has heard of it.

Also nobody can premine it, no coalition of big stakeholders can lock you out of your coins, a 51% attack is less likely feasible than for any other PoW coin, the bandwidth needed for its blockchain is smaller than most alternatives, and it's less likely to conceal unknown cryptographic weaknesses. It's kind of shitty in some other ways, though.

And eventually the math will be solved and every bitcoin will be worth zero.

Fame is part of it, but it's more that it's IMO probably the only truly decentralized cryptocurrency. Not just in terms of the nodes and miners being well spread out between organizations and parts of the world, but also in terms of its development and governance. Sure, there's a relatively small group of core contributors to Bitcoin, but they don't have much fame or personality cults around them like Ethereum's Vitalik does. They are really just restricted to maintaining and adding well-agreed-upon new features to Bitcoin. Eg when Segwit happened, a lot of miners held out on supporting it for a long time becasue it was a bit controversial. Meanwhile with Ethereum, if Vitalik really pushed for some controversial change, it would probably happen. Once you go further down the list than Ethereum, things get really bad, with many cryptos' development being entirely driven by a small group of people in a for-profit company, with miners and users that will blindly update to the newest version regardless of what's in it.

While that's conceivable, Merkle-graph systems like Bitcoin are surprisingly resilient. It's been almost 20 years since MD5 was thoroughly broken, but still nobody has published a second preimage attack. For SHA2 and SHA3 nobody has even published a collision attack. And SHA-256 (what Bitcoin uses) is post-quantum-safe (Grover's algorithm still needs 2¹²⁸ time) though AFAIK there isn't yet a post-quantum cryptosystem deployed for signing transactions, which will require a hard fork.

Presumably if quantum computers (or better DLP algorithms on classical computers) start breaking keys, that will become a priority.

So I think there's an excellent chance that even if the math is solved Bitcoins will retain their value. Perhaps even without many of them getting stolen in the process. This is a big difference from many other uses of cryptography; if someone breaks IDEA 20 years from now, they can decrypt your PGP messages from the 20th century, and there's nothing you can do now to prevent that.

Eth famously forked and reversed txns due to someone getting scammed.

the fact that eth classic was created from this incident and still exists does inspire some confidence that ethereum's governance is somewhat decentralized also, to be fair.

And IIRC it wasn't a "scam", it was a bug in a smart contract.

To me its inevitable. And just a matter of time. Any year there could be a breakthrough that quickly leads to missing math.

We still don't know if P = NP. You seem peculiarly certain it is, which is odd given that most of the people who study the topic strongly suspect otherwise. They could of course be wrong, but what makes you so sure?

Yes a smart contract bug. Hacked might be a better word. Or outsmarted?

Fame and security. Bitcoin is the hardest crypto to attack socially and economically.

ETH forked because the contract was poorly written and they didn't want to honor the contract because their buddies would have lost a lot of money and the project would have gotten an egg to their face.

They would just patch the software.

That's true, but you could say the same thing about a Van Gough painting. There are lots of old pretty paintings. But if you paid $xxm for your Van Gough you can be pretty sure its still worth a lot in ten years. There are no guarantees. But that's not just true of Van Goughs and bitcoins.

Assuming P != NP we still don't have any proof that sha-2 etc can't be reversed (obviously there is a loss of data). It's implausible for now but someday I guarantee we will have the math that makes it trivial. It does not require P = NP.

You can't patch the rules for the existing bitcoins. People would have to move them to new rules.

That is not necessarily how this works. The only thing required to happen is that a super-majority of the miners running the bitcoin software voluntarily update to a new version. This is how changes have been done to BTC before.