Bitcoin Cash has wealthy entities behind it capable of lifting that market up to record highs. They are buying their own orders up, and directly the market, which isn't them dumping their  Bitcoins for BCH, but them tricking noobs into thinking like that. It's nothing more than a game. If these entities would really end up selling all their Bitcoins, they would lose their significance in the Bitcoin market, and thus be major holder of a worthless altcoin -- they aren't that stupid to do so. Their wealth in Bitcoin grants them all these possibilities, and without it, they are nothing. It's not the first time that BCH has increased significantly at cost of Bitcoin, and it won't be the last time. They use the weaker momentum to strike, and that's something helping them till Bitcoin goes up again.