Well, before they can buy bc they need to take the shitcoin and trade it for btc then to bc incurring 2 trading fees. It makes more sense to mine with a multipool that mines shitcoins for btc, then you get a choice whether/when to buy bc. I think the idea was stupid from the beginning, not sure how to explain the enthusiasm shown by the current pump.
The whales aren't done yet pumping. I keep watching the top BC wallets grow and shrink buy millions of coins each day. One wallet grows to 4 million BC, then drops to drops to 1.5 million. Later in the day it is back at 3 million. The link below is the blockchain explorer for the top 100 wallets.
http://agran.net/bc_getbalance.php?top=100