GGGP never said that to run a law firm, you had to have practiced in every area the firm does. He never said the law firm should outsource its HR and payroll and travel, unless the managing partner had experience in those functions. He said the manager of the law firm should be a lawyer.

Elon Musk has a degree in physics and began a Ph.D. program in materials science, which is probably the second-most applicable field to automotive engineering generally (after mechanical engineering). For someone doing solar cell and battery work, materials science might be the most relevant field. So tell me why you think Musk proves your point and contradicts GGGP.

Reasonably sure EM has also used a computer and managed technical companies. Someone who hasn't used a computer in 2018 is not suitable for most jobs, short of digging ditches.