To understand the concepts of Distros you need to understand the fundamentals of Software Builds.
Linux or Windows or Any Operating System that doesn't matter ships Distros. They are a Conceptual Component Systems.
We Will talk now more about Linux as there it is often more logical as we have a larger set of possible distros.
The most Linux Distros got diffrent Compilers and Package Managers thats what makes them a distro at the core they use the same Core Kernel which they may or may not adjust to work with the rest of the distro that they ship.
Why do they even integrate so much software? They do that to speed up your local builds and dedup dependencies. That was needed for Historical Reasons. That Process got identifyed as False!
We have better alternatives to reach wanted goals but with much better effects:
Descriptive System Setup got identified as key element but it should be done in a dynamic language that also got identified as key element.
ECMAScript with its module syntax including the fundamental ability to modife the loading of modules showed that it is the successing system to reach that goals
it got our most core principles covered out of the box as platform like isolation and security for zero trust.