It's very surprising the talent pool they're pulling from to me as someone that doesn't have training in physical engineering beyond control systems and computer vision. Two of my friends who received Chemical Engineering degrees and were advancing in their careers at Exxon are now working at SpaceX with higher salaries (but no pension) as well as a couple friends from college who were in Systems Engineering. All of these people I'd classify as very good engineers as they have all been very high achieving in their fields in college and professionally. Oddly enough both sets are married. I wonder if that's a hiring strategy.

edit: now that I've thought more about it Chemical makes sense since they have chemical rockets and they both have industrial scale manufacturing experience.