You bring up an interesting point. If Nvidia had so much revenue dependent on the mining boom as we all accept, why in the world did they not know about the now happening POS event. They seem, from the outside to be caught almost by surprise. Not even a single employee tasked with properly monitoring a billion $ market?
Because mining altcoins at pre-May price levels would still be very profitable. POS isn't what ended the miners buying spree. It was the crypto crash.
