I have a hard time understanding the link between the feature of a key server and block chain. This is a great idea to simplify PGP, love it, but nothing to do

I have a hard time understanding the link between the feature of a key server and block chain. This is a great idea to simplify PGP, love it, but nothing to do with block chain at all. Basically a public key server where all recipients have their public key available to send email too and have proton mail use it automatically.