Why it's going up? Well, there is a big possibility that only one of them (btc or bch) will survive this battle. The one with the most hashing power wins. Now, if you owned Bitcoin prior to the fork augus 1st, you're good. You own the same amount of both unless you've somehow transferred bitcoin without splitting it up first.

Another reason its going up is because of ultra high transaction fees for bitcoin. And also that more people realize that perhaps BCH is more similar to the bitcoin Sathoshi had intended than Bitcoin core.

If you want, read my earlier post today
https://steemit.com/bitcoin/@scandinavianlife/big-news-bitcoin-cash-gets-added-to-coinbase-as-bitcoin-core-falls-here-s-what-i-did-and-why