My evidence is the git commit log: https://desuarchive.org/g/thread/84460945/#q84481507

This doesn’t even include the XFree86 CVS commit history and older, which accounts for most of the code in X.org. Some of those people may actually be dead now.

>AFAIK xorg always only had low 10s of active developers.

There are 38 people with 100+ commits, which obviously counts as a major contributor.