Maybe this dump is connected with revival of segwit2x hard fork. Fork is scheduled for 28.12. https://bitcointalk.org/index.php?topic=2595620.0

   So, the Big Guys drop their BTC, price drops, the New Guys start to panic sell, price drops further more. The Big Guy buy BTC at discount prices, and accumulate more then they had before.

   So they have better position for 28.12. segwit2x fork. Standard procedure.