It's only scanned models animated with Mixamo (I recognized the mocap directly) and duplicated with a cloning/particle system. There's nothing really "procedural" about it.
It can be done manually in Cinema 4D, for free and relatively fast.
The easiest way:
1. Create your characters and looped animation in Mixamo (https://www.mixamo.com/).
2. Export them in Fbx.
3. Load the files in Cinema 4D, adjust the textures, make variations (colors, scale, speed, ....).
4. Clone these characters with Mograph or Xparticles.
You could also use the characters in Cinema 4D's asset browser (Models > Humans > 3D people), load and animate them in Mixamo.