Most people have two arms, two legs and a head. These limbs and all of their minute components, bring about near infinite combinations of submission holds. Even when you think it has all been done, someone has an epiphany mid-fight and pulls off some innovation that makes us go — Whoa, that's a double armbar, all the way.
You can see here from human pretzel north-south position that there are two arms wrapped up, getting yanked on to try and go down in submission history. The only other double armbar submission I know of in MMA was Alexander Otsuka vs Mike Bourke at PRIDE 11.
So bright. So vivid. So intense. Look at that double armbar. Ok, Debbie Downer, no, Hu Dan Dan didn't actually submit Kang Jin Xi with it, but it's still super cool. Not everyone's inventions always work out on the first try anyway. This just paved the way for even more armbar innovation across planet Earth. Ronda Rousey is somewhere, pleased.