knowing the right person to ask is hard.

If you manage these people, it is literally your job to know.

For senior management, it is usually it is your job to hire people who know or help you know( a.k.a consultants )

It is not humanly possible to be knowledgable in all the fields of people working directly or indirectly under you. Good managers are not always technically knowledgable . It is useful skill to have, neither it is most important nor is it even essential.

While bad managers tend not to have the knowledge, the worst managers are strong technically but don't have other critical skills needed for the job.

Nobody expects you to know everything.

But as a manager, you need to know what your organization is doing and you need to know who to ask.

That is, by very definition, the job of a manager.