Bitcoin Cash is the solution to one of bitcoins biggest issues, transaction scaling or how to handle the increasing demand for transaction processing on bitcoin.
Bitcoin introduced SegWit or segregated witness which is the process by which the block size limit on a blockchain is increased by removing signature data from Bitcoin transactions but not everyone thinks this is a good idea.
So Bitcoin cash was created without SegWit instead opting to simply increase the block sizes from 1mb to 8mb allowing more transactions to fit into a single block thus ultimately reducing transaction fees.
Now this is a bit like increasing the number of lanes on a highway from 4 lanes to 32 lanes which sounds great in theory but this also incentives more junk or spam transactions, something having a high cost per transaction effectively prevents.
If the killer app of blockchain turns out to be store of value then Bitcoin probably be the winner but if for whatever reason people value a peer to peer payment system then Bitcoin Cash with its lower transaction fees might just push ahead.
Also consider that right now with record high prices for bitcash that mining is much more profitable than good ol BTC and once difficulties iron themselves out we might just see another yoyo back to pre-cashening levels.
Interesting to also note that bitcoin gold futures are also up by multiples and this all might just be a reaction by the satoshi conservatives to make bitcoin easy and cheap to transact not just digital gold or store of value.