Their software had bugs that could cause a stack overflow and critical data wasn't protected. Sure, it might not be the real cause, but it's a pretty likely can

Their software had bugs that could cause a stack overflow and critical data wasn't protected. Sure, it might not be the real cause, but it's a pretty likely candidate. It's not like these errors are unlikely in general. Apart from the occurrence of the stack overflow itself (which is hard to directly observe), the rest of the problem was demonstrated in testing. Memory corruption in the wrong place kills a certain task and that causes uncontrolled acceleration.