I’m not sure your idea of 70s and 80s IT infrastructure is historically accurate.

50 years ago it was technically impossible to rent time on a mainframe/server owned by a third party without having physical access to the hardware.

You, or to be more accurate, your company would buy a mainframe and hire a mathematician turned programmer to write the software you need.

Even if – later in the course of IT development – you/your company did not develop your own software but bought proprietary software this software was technically not able to “call back home” until internet connection became standard.

So no, computers did not start with “the corporate elite” controlling them.

Computerized cars, on the other hand, are controlled by their manufycturers since they were introduced. There is no open source alternative.

Open standards for computerized cars would be great — but I’m very pessimistic they will evolve unless publically funded and/or enforced.