Drupal core would be split into the required components, with all the optional components separated out, along with these 10 or so critical contrib modules to become this base distribution.
Each of these components has a driver, someone who looks after their component, as well as co-drivers who might only be focused on improvements for a certain version or adding new features. This group of people talk regularly to coordinate efforts and are steered by the distribution’s (Drupal’s) driver (Dries or someone else who manages a specific release).
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