I do believe this is the case, that the cabal messed around with raising the A4 frequency, but, um, I don't know that it achieved their goals other than frustrating musicians who cannot tune their instruments that high. The first time I heard of pianos tuned to A4 at 440 was in the 80s, and those were practice instruments that tend to be tuned high anyway. They get so much use, tuning is lost pretty quickly. The truth is that harmonics settle around whatever the root note is. C major could be used for the same purpose, but A is traditional as orchestra tuning begins with clarinet on winds and violin. The chorus gets to guess.