There are existing algorithms that do that. E.g. Paxos, Raft, 2PC. Real breakthrough of Nakamoto is devising a scheme where whole network is protected against

There are existing algorithms that do that. E.g. Paxos, Raft, 2PC. Real breakthrough of Nakamoto is devising a scheme where whole network is protected against Sybil attack. I.e. there is no need to don't trust or register parties who participate in the network. All elements of Bitcoin, such as proof of work, crypto ledger, merkle trees, etc were already known. Nakamoto combined them in a way which solves an unsolved problem.