Rakudo Star is a release targeted towards end users (if I'm not mistaken). As such, it includes a number of useful modules that can be used in a wide range of projects.
But how does the team behind it decide which modules to include? Do module developers talk to them and ask for inclusion, or do they look at usage statistics and include the most popular? Or is inclusion completely arbitrary?
What process should one go through to get their module included?
The collection of modules is in the star repository, includes as sub-modules of the repo. I haven't seen any kind of description of what modules are installed there and why, but I guess using the issues and/or pull requests is the way to go. In fact there's this closed issue which points in that direction, including a reference to ecosystem statistics, so I guess regarding your three questions.