The blockchain is just a hash tree, which was patented by Ralph Merkle in 1979. Using blocks of financial transactions as nodes is a new application, but not so different to the idea of propagating rights down the certificate chain you find in PKI.
The blockchain is not just a hash tree. There's other features that mesh together in the blockchain. For example a proof-of-work system that allows bitcoin to be distributed and trust-less by preventing Sybil attacks. While using rewards for this work as the sole means of money creation was anticipated by others, the automatic means of adjusting the cost function is a Satoshi original and very important to the success of bitcoin.
