Why again blockchain?

#1

When I was going through the whitepaper, Blockstack migrated from namecoin to bitcoin. Though namecoin and bitcoin store data within its own blockchain transaction database. Yeah I read the article that what was the issue in namecoin. But what is the main purpose or benefit(s) to use blockchain again? There are other networks as well like DAG, Holochain, Hashgraph.

Blockstack is not a DAG
#2