I think the parent post is recommending an orderly breakup as opposed to a collapse where society is left to pick up the pieces.

The issue comes back to foreign competition. As much as Glass-Steagall made sense to some, it was repealed because US banks faced increasing competition from European banks that were able to bundle advisory with retail bank deposits. Unless everyone takes similar position globally (or we block foreign bank access to our markets) it’s hard to justify a handicap on the home team.

Banking is a sector where it's easy to win on a short term (10year) horizon and lose everything on a 20 year horizon. Ultimately if the taxpayer is going to foot the bill on the 20 year horizon then they should be able to ensure that only players obeying the guardrails are allowed to play.