Lol, I'm not fond of saying other car companies make their own cars. They do not, maybe their own emgines, and final assembly of parts they bought from Tier 1, 2, and 3 suppliers (to whom they forego profit). And then they sell to Dealers (who eat more profits), not end customers. Established Car companies are Banks that make cars, and sell replacement parts for obsolete cars. And those Banks are under duress right now. No fondess at all for this comparison.
Telsa on the other hand makes most of its own parts, all of its own software, and does no catalog engineering. If they do buy from 3rd parties, they have their own Tesla engineers embedded at the companies to ensure product compliance to Tesla's demanding specs.
Oh, and the Energy business (which no car maker has). And AI robots and Supercomputers. And sometime in the future, a ride-hailing network with driverless cars.
I'm a fan of all that.