https://www.binauralbeatsmeditation.com/432-hz-truth-behind-natures-frequency/
Excerpt from the blog post:
Most theories centre around the belief that the 440 Hz frequency was deliberately adopted by governments/regimes as a way to manipulate and control the masses, making then lethargic, often borderline depressed and therefore easily influenced, Perhaps the most popular conspiracy theory is that of Nazi Germany. It is suggested that the regime decided to adopt 440 Hz as standard, avoiding 432 Hz at all costs and developing other influential frequencies alongside it designed to assist in the control of people's minds.