Bitcoin difficulty gets adjusted every two weeks to maintain a block reward time of about 10 minutes.
Think of it this way, if there was a quarter on a football field it could take you a 1/2 hour to find it. If you had 100 friends, you would find it in minutes, maybe seconds. In order to maintain the 1/2 hour time frame to find the quarter, you would have to expand the search area from 1 football field to 100 fields.
Bitcoin does the same thing, as more miners enter pools, difficulty gets adjusted.
It appears that miners are abandoning Bitcoin Cash(BCH), and moving back to Bitcoin. Over the past few weeks, the hashrate of BCH has gone from 3 ExaHash to 1 ExaHash.
Over the past week, during the selloff, Bitcoin hashrate did dip to 4.5ExaHash but has recovered today to over 7 ExaHash:
https://blockchain.info/charts/hash-rate?daysAverageString=7
Bitcoin Wisdom is predicting that in less than 2 days, the mining difficulty is going to increase by 20%. That means if you are hardware, or cloud, mining your daily earnings are going to decrease by 20%:
https://bitcoinwisdom.com/bitcoin/difficulty
Our Antminer S7 will be reduced to about .50c/day in earnings. For $15/month profit, the wear and tear on the unit is not worth it unless you are using it for a space heater. Also our cloud mining contract will be at risk of being voided due to costs exceeding output.
Keep an eye on Bitcoin price next week, the difficulty adjustment is going to have a huge impact on everyone.