> All the good bits of blockchain, we already had in git

This is not true at all and shows a common misunderstanding of why the blockchain is useful.

The big breakthrough with blockchains and crypto currencies has very little to do with it it being a ledger with signed hashes. There are two main "good bits" of the blockchain:

- it provides a consensus algorithm to agree on a set of updates to the ledger. Not in git.

- it provides a mechanism for anyone to take part in this consensus algorithm while preventing sybil attacks. Also not in git.