I'm not in management, but I don't think it's too different from what I've heard when talking to people in management.
In the US, the first years are not so different from a master's. So, the qualifying exams feel like another filter really, to see if you're ready to move on to the real PhD stuff. And then in other countries you may not find such exams, especially if you go to places that use a different system like Europe and Australia where applicants are all expected to have a masters and more research experience.
The exams are not easy, but I think that's often not the main challenge. If you were able to focus on studying for the qualifying exams, probably you would do well. The problem is that you need to prepare for the exams while being overwhelmed by tons of other stuff you need to do.
So, I think people fail the exam not because the exam is hard, but because people get lost. Maybe they are not so motivated anymore, maybe they are not able to handle the pressure, maybe they find out a PhD is not for them, maybe they are terrible at managing their time, etc. I don't know the pass rate, but it's usually low. It's not so common for schools to make a mistake and accept a student who will not be able to handle the exam. But don't underestimate it, plan ahead, prepare in advance.