The Interstate Commerce Act, the Pure Food and Drug Act, and other federal regulatory laws were in place before that.
Interstate Commerce Act and the Pure Food and Drug Act represent the eccercise of commerce power that are miniscule in comparison to what happened in the 30’s. I disagree that both are proper exercises of commerce power (I also include the child labor cases as not within what commerce power should allow). I am no fan federal power expansion allowed under the cult of Teddy Roosevelt. Regardless, you are missing the point - commerce power, a specific and enumerated power, is not police power, which a Court can interpret expensively, no matter how much the “woke” want expansive commerce power.