They are 100% not idiots (okay, maybe 99.9%), it’s just that from the outside the decision seems incomprehensible to us because we don’t have all the information. I am sure that there were serious internal factors and ETH was the cause of them, maybe it was a problem in the locker room (ETH's ego is well known), maybe it was some scandals with the management (he was not allowed to buy half of the Ajax team for astronomical amounts of money  ). In some ways, ETH turned out to be so unacceptable that management took such a step, questionable from all sides.