Whatever the real situation is behind Bytecoin, I think it's clear that:

a) Their launch was shady and obscured from the public
b) This pump was definitely not natural, even if there is no insider trading or anything of that kind, it's still an unnatural pump that will correct in due time.

You're right, though. Who's actually buying the coins with so much volume? And where's the coin coming from if deposits are closed? Any sane trader would know to shy away from these hyped up, short term, gains. It may be possible that there are measures to artificially inflate the price of BCN during this pump.