I saw a post here I believe, generally Tesla seems to have made a car from scratch with sane decisions made when Tesla was small. I've heard engineers claim that the central compute module for Tesla has a level of integration rarely seen outside of satellites.
Large car manufactures typically have empires built inside of them for major areas of the car. Transmission, engine, suspension, chassis, entertainment, etc. Each with financial budgets, staff budgets, weight/size budget for anything in their car.... yes they literally count grams. They fight for their resources.
As a result of their org tree, that impacts the design and connectivity inside the car. Often have different networks of sensors, different CPUs, even different power delivery systems.
