it was a certain group of people with money to advertise it, with hashpower to mine it, and with motivations to overtake bitcoin and make it centralized.
the fork didn't make "BITCOIN and BitCoin CASH". the fork just made a new chain called bitcoin cash.
bitcoin is still intact and the same as before. the forks from bitcoin happened in the past too. this is not the first fork. others usually make a separate chain and make their blockchain from scratch instead of building on top of old blocks.
for example bitcore (BTX) is a fork of bitcoin with SegWit and 20 MB blocks and 2 minute block time (IIRC). you can get the airdrop of that the same as you get air drop of BCH. 1:1
some traders invested their coins in exchanges before the fork and dumped it right away.
some people who were more advanced waited for the fork and then claimed their coins safely
but majority are either scare, confused, or don't care about claiming it yet.
some also think it will go up so they are holding.
if it were anything but the above, BCH price would have been 0 by now!
so technically, SPLIT COIN to 1 & 2 - DUMP coin 2 - MAKE MONEY -PUMP Coin 1.
simply because if you have BCH and want BTC you sell BCH on the BCH/BTC market and get bitcoin in return and pay fees only once.
you never sell BCH for USD then use USD to buy BTC. that is dumb and you will end up paying 2 trading fees!
in other words it had no effect on bitcoin price.