Questions about governance and the upgrade process

Trying to understand some fundamental concepts which I did not find addressed in the Cosmos docs.

  • Why does the network upgrade require to restart at block 1? Why couldn’t cosmoshub-2 pick up from the previous history?
  • What happens to the history of cosmoshub-1? It’s still available on block explorer and I’m curious who is storing that data and if it’s still considered immutable?
  • On proposal #5 still being in voting period. What’s the point of having a fixed voting period if it can be overridden by social consensus? Are there discussions to improve this?
  • Why does proposal data migrate to the new Hub, but not transaction?