Using follow-up & coaching questions will develop your skills as a manager, and support communication within the organization.
Asking why will get the problem solved faster, in the short term. However, the problem and similar problems will come back to you, because you solved them. Asking ‘when’ will create progress with the team member and you; leading to learning.
Your best project manager comes to you to help with personality clashes. They share how strong personalities are getting in the way of work, and asks for your advice on how to fix this dysfunctional team. Rather than asking why – which will move the work onto your plate – ask a series of ‘how’ coaching questions.
Using personality or behavior assessments (DiSC, MBTI, Big 5, etc.) continually reinforces the false belief that people are the problem and they are not good enough being who they are.