At one point in my life I was working on a massive Android AOSP fork that itself had lots of variants for different downstream devices. Custom drivers, specialty services, etc. Thousands of people were actively working on all parts of it, and it had been around for at least a decade.

There was incredible tooling around onboarding, local dev, testing, PR management, CI/CD, and post-release telemetry. Almost everything was automated. All code was reviewed at least once, and sometimes more for critical components. It was an immediate rejection if there wasn't sufficient test coverage. Big subsystems took months to architect, build, and deploy.

Nobody got to cowboy things and just push to release. It was much slower than a solo or a few people at a startup. The whole point was consistency and predictability, and you could see why.