If the sensor had just stopped responding, there wouldn’t have been any problem. The planes would keep flying, the sensors would get replaced, and everyone would be fine.
What happened was that the sensor gave erroneous readings. The MCAS system reacted to those erroneous reading and crashes the plane.
With two sensors, you can detect failure. It’s very unlikely that both would fail simultaneously. If they did, it’s very unlikely that both would provide the same erroneous readings.
If the sensor had just stopped responding, there wouldn’t have been any problem. The planes would keep flying, the sensors would get replaced, and everyone would be fine.
What happened was that the sensor gave erroneous readings. The MCAS system reacted to those erroneous reading and crashes the plane.
With two sensors, you can detect failure. It’s very unlikely that both would fail simultaneously. If they did, it’s very unlikely that both would provide the same erroneous readings.