Waitbutwhy has some interesting posts about what they see as the role of each company. The Neural link one summarises them at one point (though is an enormous article, and a great one).

https://waitbutwhy.com/2017/04/neuralink.html

As an aside, they have some really wonderful long form content. I love the 1 to Graham's number posts (a two parter) https://waitbutwhy.com/2014/11/from-1-to-1000000.html

That's good news for earth. You often need a closed loop product lifecycle in space, since you can't throw away and source new parts and materials without great cost. Any spinoffs should help us close open loop systems down here on earth.

I believe the standard working hypothesis is that Elon Musk is a lonely alien trying to get home, and started a car company because it seemed nicely inconspicuous.

s/started/joined/

Okay, but no quibble re. the lonely alien part?

I'm agnostic on that :)