Regulations aren't fixed. They aren't laws. They are reverted just as easily as they're made in the first place. Regulations are executive branch power only. If you're worried something you care about might change when the political winds change, you'd write up a bill doing exactly what the regulation does, and get it signed into law. They could have done this in a day, and they didn't.
Democrats were either incompetent at predicting the GOP would unwind this when they said they were gonna. Or they liked the idea if it being unwound and being able to blame the GOP for it.
And like I said, not their first day at the rodeo, so the former is impossible. They are definitely not incompetent, they definitely knew the regulations would be unwound. And they definitely did nothing about it as if their either didn't care, or they liked the idea of using it to rile up their base for campaign donations and votes.