The American legislative system is bizarre.
To begin with, Congress is accorded very little power by the constitution, with most of it resting with "We the people" or the states.
This however, doesn't pattern match with the amount of power some people (typically progressives) _think_ the Congress or government _ought_ to have, or the amount of power Congress _wants_ to have (as much as possible), so we see BS things like the abuse of the Commerce Clause loophole to justify any Congressional intervention.
Now, you'd think that with all this power that they have loopholed their way into, they would actually exercise it, but that doesn't actually happen, because they are permanently gridlocked and can't pass any damn shit unless it's part of a giant 1000-page omnibus bill that has 100 unrelated things clubbed together based on whatever horse-trading they manage to do one day before the govt shutdown deadline.
So what actually happens is that the actual rule-making is done by the executive, in the form of these government agencies, which ideally should be enforcing things that the Congress has passed, but effectively are given pseudo-legal power through a variety of judicial interpretations (eg. the Chevron Doctrine) that can be overturned by the next Supreme Court as trivially as they were written in.
All in all, you get a massively dysfunctional system where regulatory agencies act as effectively unelected lawmakers, with the actual lawmakers doing jackshit, and the judiciary effectively supporting these shenanigans through capricious rulings.
And while doing all this, lawmakers can conveniently ramp on the rhetoric during campaigning because they know they don't actually need to do anything. They didn't even pass abortion-related legislation for 50 whole years, because they could use that division to reap votes every election cycle.