Decentralization: Every node which maintains the network has a copy of the ledger. That creates redundancy and fault tolerance (i.e if a node fails or stops working, the rest of the nodes can keep maintaining the network without interruption).
Blockchains are digital organisms. As organisms evolve though changes in their DNA, blockchain protocols evolve through changes in their code. And like biological organisms, the most adaptive blockchains will be the ones that survive and thrive.