Blockchain is a ledger that is not managed and controlled by only one particular party or organization, but the blockbook is publicly distributed and managed by millions of computers around the world at the same time.
Every computer in the network can view or add notes about recent transactions into the Blockchain Ledger, this is the main strength of the technology, so it is impossible for anyone to delete the Blockchain Ledger because it is not managed by one person and one place, but it is managed globally at the same time.