Why did Bitcoin Cash modified its difficulty adjustment?

Since Bitcoin Cash hard forked from Bitcoin, it uses exactly the same mining algorithm. This meant Bitcoin Cash had to compete for mining power. Initially, Bitcoin Cash had only 5% of the mining power of Bitcoin. If there is not enough hashpower to mine blocks it would be no longer possible to make transactions on Bitcoin Cash network. In order to survive, Bitcoin Cash has implemented an algorithm called Emergency Difficulty Adjustment (EDA) on 13th of November 2017 that would adjust the difficulty of Bitcoin Cash mining. If there has not been mined more than 6 blocks in the last 12 hours, the difficulty would be reduced by 20%. EDA was evaluated on every block. If there weren’t enough blocks the difficulty could reduce very fast. With less difficulty it was easier to mine Bitcoin Cash.This raised the profitability of Bitcoin Cash mining thus incentivising miners to mine Bitcoin Cash instead of Bitcoin. The problem with EDA was that it caused erratic block time fluctuations, ranging from 61 blocks in a single hour which means 1 block every minute to a single block in 4 hours. Bitcoin Cash should have 1 block every 10 minutes just like Bitcoin does. The problem with EDA was that it messed up the coin issuance schedule of Bitcoin Cash. Every 210 000 blocks, both Bitcoin and Bitcoin Cash halve their mining reward. When Bitcoin was first created the mining reward was 50 BTC, after another 210 000 blocks, the reward became 25 BTC. Today the mining reward of Bitcoin and Bitcoin Cash is 12.5 BTC.  With its erratic block time, Bitcoin Cash accelerated to 55 days ahead of Bitcoin, meaning that Bitcoin Cash will halve its mining reward to 6.25 BTC before Bitcoin.  In that case, everyone will mine Bitcoin instead of Bitcoin Cash.

This is why Bitcoin Cash hard forked on 13thof November 2017 and introduced a new difficulty adjustment that will keep its block time consistent at every 10 minutes. Hard forks don’t always end up with chain split. If the community as a whole agrees to the upgrade, there will be no new coin. In this case, everyone knew that Bitcoin Cash desperately needed a new upgrade so everyone supported the hard fork. New coins are created only when the community is divided and have different ideas of how to continue the project in the future. Therefore, they have to create a new coin in order to carry out their own version.