The insane thing is Chevron deference was the original conservative position. Under the Clean Air Act, factories had been regulated one way, but when Reagan was elected, his EPA switched to a more business (and polluter) friendly interpretation. The National Resources Defense Council sued Chevron and the EPA over it, and Chevron deference was cheated in a unanimous opinion (although 3 justices had to recuse), which said regulators could make any reasonable interpretation of the law.
Another irony: one of the original defendants was Neil Gorsuch’s mother, ego was EPA Administrator at the time.