>He has to broadcast his public key for this [...] through a public and decentralized ledger.
Yes, but then he also has to broadcast the transaction linking his identity and public key. He could do this on twitter, but that is not a secure and tamper proof ledger. So he creates a second blockchain to advertise the transaction. But then he needs to advertise the second blockchain's transaction in order to link his identity and public key. He could do this on twitter, but that is not a secure and tamper proof ledger. So he creates a third blockchain to advertise the second transaction...
Yes, but then he also has to broadcast the transaction linking his identity and public key. He could do this on twitter, but that is not a secure and tamper proof ledger. So he creates a second blockchain to advertise the transaction. But then he needs to advertise the second blockchain's transaction in order to link his identity and public key. He could do this on twitter, but that is not a secure and tamper proof ledger. So he creates a third blockchain to advertise the second transaction...