I think you may be confusing proof of work with blockchain as a general principle. (I'm not a fan of this cryptocurrency tech anymore either, my comment is purely about the technical properties which can be interesting to study.)
No, GP is right. Without Proof of Work blockchains have no leader - think about Git repo with multiple branches: which one is main? Nothing in blockchain itself determines this, only we, humans chose to name one of them "main" (formerly "master").
> Without Proof of Work blockchains have no leader
But, proof of stake?
proof of stake blockchains certainly have leaders. MEV doesn't exist if there aren't designated block proposers