The list is ranked in a completely transparent way. It's anything with the help wanted tag, ordered by number of stars.

So this isn't some sneaky Microsoft thumb on the scale, the way you appear to be implying. Simpler than that: I doubt many projects know about this list (I for one just saw it for the first time), and since GitHub put it together, Microsoft codebases got the memo to add the tag.

If you want to see other popular projects at the top of this list, open up a PR to have them add the tag.