Well, it was originated by a Japanese player (can't remember the name off of my head) who ran 3-4 Cobalion I believe but only 1 Kyurem. The reason Kyurem is more of a focus here is because of Reshiphlosions's popularity, but I feel that Kyurem won't come out on top of Reshiram because Reshiram OHKOs Kyurems with a PlusPower while Kyurem only 2HKOs active Reshirams and 5HKOs benched Typhlosions and Reshirams assuming no Afterburner damage. This means that unless Kyurem starts attacking turn 2 and Reshiphlosion can't attack/draw a PlusPower for a while, CaKE can run out of Kyurem/energy before winning. This is why I feel that Kyurem alone, with no Vileplume or reliable energy acceleration (Electrode's reliability isn't too good since it is very luck based) doesn't beat Reshiphlosion reliably enough, and that why something like SEL is probably better with Electrode and Cobalion (it also works way better against Durant, and with Electrode blowing up the top 7 cards of your deck Durant is a really tough matchups that Kyurem does very little aganst).