Why would a generalist be wiser than somebody who is able to go into depth and understand the ugly details of a project? That is what the T-shaped thinking is a

Why would a generalist be wiser than somebody who is able to go into depth and understand the ugly details of a project? That is what the T-shaped thinking is about. Elon Musk is a great example who is able to answer deep technical questions on many subjects, and I think he needs people who understand their own project deeply, not ,,short fat'' engineers.