Mellon was wrong because he didn’t understand the non-linear dynamics of a central bank/fiat currency based system. Only Irving Fisher did at that time and he was not ignored, but merely told he was wrong...by people who didn’t understand his math.
The older crowd came from the world of money panics and metals based currency. Different rules.
America is like a beaten wife....Too eager to believe in more chances to get it right...UNTIL THE DAY SHE IS ALMOST BEATEN TO DEATH...THEN SHE BEGINS HER CLIMB OUT OF MISERY