This is a good podcast on the old regime: https://www.npr.org/transcripts/696337392

Summary of the old regime: Mergers that lead to 5+% market share were blocked.

Then the "consumer harm in terms of prices" was adopted. Which swung the pendulum the other way. That is the fundamental economic policy now. Which has lead to abhorrent results.

I wrote a comment on previous post that was about how consumer harm standards have warped the discussion on tariffs: https://news.ycombinator.com/item?id=48096236