Cozy relationships between the FAA and manufacturers, executive orders requiring them to 'collaborate' with manufacturers, evidence suggesting retaliation against whistleblowers, etc. there were significant investigations after the the MCAS tragedy. And they lost a lot of credibility as leaders in regulation when they waited to ground the max after the crashes while others took the lead.

Edit: Replying to the edit - oh come on HN dont downvote their question it's a reasonable question, my original response didn't link any articles.

The regulation doesn't specifically have to get rolled back. In this case a large part of weakening regulations is shifting to allowing the manufacturer (Boeing) to regulate themselves and allowing (or forcing) ties between regulator and manufacturer to get too close.

https://www.nytimes.com/2019/03/26/us/politics/boeing-faa.ht...