There is no need for a huge list of reasons. First of all price dropped because there was a hash war going on in bitcoin cash hard fork times and during those times both sides sold their bitcoins and bitcoin cash in order to fuel the fight and become the winner of the war.
It's easy to think like that, but how do you know that's actually the case? I think the dump was more related to the overpriced market at $6000 levels, and the steep reduction in Bitcoin's difficulty.
Lower difficulty means more coin inflation. More coin inflation during an overvalued market is almost a guarantee that prices will go down. Traders saw it coming in and might have liquidated some of their holdings.
We have seen 2 billion in volume type of low amounts which is really low considering only couple months ago someone bought 500 million dollar worth of bitcoin with tether and the price only went up a slight bit.
Who is that someone? I can't recall anything like that and I very much doubt that anyone used or owned 500 million USDT to buy Bitcoin with. Most of the circulating USDT is well distributed amongst dozens of exchanges.
I do remember having seen 11k BTC buy walls on Bitfinex around $7700 this year, but that's very likely Bitfinex itself spoofing its order book. No one in his right mind would ever have that much value on such an exchange.