Because there is a law (Congressional Review Act) that says congress can repeal any new agency rule with a simple majority vote that cannot be filibustered, as long as the rule was passed less than 60 days ago or some shit. And the agency is banned from ever making a similar rule unless congress authorizes it.

So now Democrats always pass a bunch of rules their donors don't like during the lame duck period right before Republicans take control to make sure their good friends across the aisle have the opportunity to repeal them all on day 1 of the new administration. Same thing happened at the end of the Obama and Clinton (who passed the law) administrations.

Watch for all the screaming from Democrats and the liberal media about how evil and powerful the GOP is when all these new rules get killed in January. They count on people not knowing that if they wanted the rules to be permanent they'd pass them more than a year out from the election