Going by the definition given in the wiki you’ve linked, a Sybil attack is about creating many fake identities to gain disproportionate influence in a network. A 51% attack in blockchain terms is specifically about controlling the majority of the network’s mining/staking power to override consensus.

So I'd say they're not exactly the same.

Someone amassing 51% of the network would probably want to do so under some fake identities so others don't realize what's about to happen. Not the same, but probably related.

Lol, there's no such thing as "fake identities" here. You just run more miners with different payout addresses for mining. But there is no "fake"

> You just run more miners with different payout addresses for mining.

That it's dramatically easier to conceal your identity doesn't mean concealing your identity isn't useful.

It's the same failure mode as a Sybil attack, but it's called a 51% when there's the additional assumption of the hashrate being hard to obtain and evenly-enough distributed to mitigate sybiling, and that assumption is being violated.

A Sybil attack is about having many identities in systems which make such identities count for something, blockchains are designed to avoid that attack by saying "identities don't matter for consensus, only raw 'work' does". a 51% attack is therefore analogous to a Sybil attack but not the same thing.

Byzantine Failure seems more appropriate.