Kimarite
en.wikipedia.orgI think this level of detail partially comes from the long history behind this sport. The participants have had 1000 years (give or take), to hone the craft and explore every single aspect of the discipline. That's how you get such a long, more-or-less exhaustive list of all possible ways of winning a match.
Parallel to this, it's really impressive to see how the average skill level changes in various sports as time passes. Two examples that come to mind are:
1. Chess. Due to lichess and the Internet generally, your average chess player is a lot better informed than people a couple of hundred years ago.
2. DotA2. The average level of play has been steadily increasing over years, to the point where a 2k MMR player now is around the skill of a ~3-4k MMR 5 years ago. Techniques that were considered highly sophisticated when the game was just starting are now considered fundamentals that every player should understand.
Excellent points, though I think this "law" (dunno what's better term for this) can be applied for almost every discipline, not just games.
Unlike a western style wrestling ring, which has plywood over springs or foam padding under the canvas, the Dohyō is rock hard packed clay. When you go down in a Dohyō it hurts. Even the straw bales are packed rock hard.
I like how the simple rules create a complex universe of techniques. I don't think I'll ever participate in a sumo match but at least I can play some Go, which shares this quality :)