They probably have. A large problem in sensor fusion is: you don't always know which sensor you can trust. For example, in this case it probably would have helped to reject IMU and rely on doppler radar altimeter. But what if it's doppler radar that for some reason return an incorrect value that indicates that vehicle is a lot higher than IMU?
It's reasonable to assume that if you're still moving and apparently underground there's a problem with the sensors, and therefore it's best not to do anything rash - like starting the landing sequence.
This does sound like a rookie mistake, and I'll bet there's a dev somewhere saying "Oh crap" a lot because of it.
It's also a hardware design problem. NASA's human missions have a weight budget that includes multiple redundant systems. I have no idea if this probe had three of everything, but missions that do are more likely to be successful.
More subtly, I'm curious if the sensor failed or maxed out. The kinds of forces that would max out the sensor might also max out the probe. So it's possible it was already doomed after they were encountered.
