It's an engineering mindset. The exact same mindset you use to design something is the one you can use to organize something, for it's all about "allocating matter" at the end, be it metal, be it resources.

One of the key aspects of a good engineering project is task division and cohesion: one team will design this section, another this one, etc. So it's not only the mindset needed to design a bolt but the mindset needed to think where it goes, who works with this next, what about costs? logistics? etc.

So, all what's needed to be efficient is already there. The key to efficiency is not about getting it but about not ruining it.

The key to his success is thus in this phrase: Too many MBAs ruining companies

People was extremely efficient before, that's how extremely sophisticated planes and cars where designed with pencil and paper. The problem started when the MBA corporate culture began to corrode everything. A culture of accommodating people based on their self-perceived importance, not their usefulness.

So, Musk is simply getting back to basics. One of the reasons I admire him and trust him is that, with an MBA sub-culture already in place, it takes great humility to take yourself out of the way and let people work. The MBA sub-culture does the exact opposite out of ego and the never ending need to justify a job position that should not exist.

This "anit-MBA" policy (aka "rub no one's ego" policy) is perfectly summed up in is anti-handbook" manual.