The reason Chevron likely compelled the Executive Order, at least in part, is because the Trump administration likely views the ability for agencies to self-resolve ambiguities in their own rules as bad and potentially obstructive to their agenda.

For example, an agency might self-resolve an ambiguous rule to say they can’t be fired or similar, which would directly conflict with what the Trump administration wants to do.

While it was overturned, perhaps there are fears of other loopholes that they see that can accomplish this beyond simple case law.