What is the biggest challenge you have faced on your projects?

The reason PMs struggle with the ability to question the team is the lack of domain knowledge. Many organizations consider project management a profession in its own right and those who practice it don't necessarily need experience in other domains, not even in the domains of the projects that they are supposed to manage.

The advantage of this approach is that the PM is highly skilled in project management but he will never be able to acquire enough domain knowledge in order to be able to lead a team. The only way you can get enough domain knowledge is to get your hands dirty and work in a hands-on role, something that most PMs will never do.

In order to be easier the PM who does not have solid domain knowledge acquired from a hands-on role should accept the idea that he is an individual contributor like the rest of the team members and he should use his project management skill to help the team succeed.

Those who consider themselves leaders, mentors, captains, coaches, etc will feel powerless when the team members ask them for directions and work instructions and they are unable to provide these things. The team members would see this as a weakness and would not consider the PM as their leader but just an annoying character that just asks them for status report.