when some groups pumps an altcoin, they do it to make money. in other words they pump it so that they can dump the coin on top near the peak not to just pump and then watch it go down! that doesn't even make sense.
dumping on top means they made a lot of money while gullible newbies were buying BCH thinking it is the "real bitcoin"!
I agree, pumping a price without selling at peak doesn't make sense, but what the BCash camp is doing doesn't make sense in its entirety. They really believe that their version of Bitcoin is Bitcoin, and for that reason kept accumulating more regardless of how hard people kept dumping. In a matter of like 3-4 months, Bitmain's BTC holdings shrunk with just under 15,000BTC.
Let's do a quick calculation;
31 DEC 2017; BTC holdings ~36,900BTC.
31 DEC 2017; BCH holdings ~841,900BCH.
31 MAR 2018; BTC holdings ~22,100BTC.
31 MAR 2018; BCH holdings ~1,021,300BCH.
The average BTC/BCH price during this period ~0.13BTC which loosely calculated could have accumulated Bitmain 114,000BCH + 40,000/50,000BCH from their mintings returns ~164,000BCH in total.
841,900BCH + 164,000BCH = 1,005,900BCH, which is pretty close to their balance on march.
Further accumulation becomes visible once they release new balance figures.