Let me fix it for you
"So not content with building the cars completely from scratch,"
Tesla as a company does not have anything to do with Musk, neither did first Tesla Roadster.
Fremont factory is an old assembly line of GM and Toyota closed in 2009 and sold to Tesla.
Chassis is developed by Lotus.
Electric motor is from Taiwanese Fukuta.
Batteries are from Panasonic (yes, Gigafactory ones will be as well, if it ever starts production).
Controller is from Chinese manufacturer of electric buses, can't be bothered to look it up now, BDY ?
What did you say was built from scratch there ?