They knew a dual/multi-sensor system would be required. They aldo knew putting one in would have mandated simulator training; and they had to avoid that at all

They knew a dual/multi-sensor system would be required. They aldo knew putting one in would have mandated simulator training; and they had to avoid that at all costs. That's why the MAX accidents are so notably engineering failures; the industry knew what needed to be engineered, but business shot it down, and forced them to build something fundamentally unsafe in the interests of maximizing profit, and not sweating the product in the box.