Did they? I wasn't there. But a reversal of Chevron doesn't necessarily mean that the courts get to do what they like. It may mean that the courts simply get to gut the bureaucratic state and kick the can to Congress -- that what's not forbidden by statute is allowed rather than that the courts act as regulators. There will be lower courts who will want to push their role as regulators, but the SCOTUS seems uninterested in playing that game given its "major questions" doctrine.

It would be very strange for the court to create the major questions doctrine then impanel itself as the ultimate regulator.