Tesla architecture might be a mess (very likely), but I bet a lot of money that among car companies that make billions in revenue their architecture is not that messy in comparison. If you consider the horror stories you hear from other car companies and their attempts at software.
I bet most other car companies do very little software dev in-house. Just tons of outside vendors all providing different pieces.
I hire a lot of folks from auto industry. Many of the bigger players do most of their stuff in house. Most of it is... cobbled together quite poorly.
That is surprising. They must be working under heavy constraints for it to be as poor as it is.
You'd be surprised
From my prior experience in a big car company. A lot of us are getting better as well, remember that there is baggage accumulated over the years. Like most things, this takes time. This bureaucracy be shed overnight, it is a painful metamorphosis. I know of systems of record where developers are close to retirement, devices which are fabricated by vendors. Every CIO change swings between "we are a car company, outsource" vs "software is eating the world, insource". Sure enough things are changing for the better.
I have a friend who's contracted to write some code for Tesla and can confirm. They have certain things that are built well, but sooo much is spaghetti on spaghetti.