The Bitcoin Fork in August 2017 resulted in 2 separate chains, Bitcoin (BTC) & Bitcoin Cash (BCH). Miners now have a choice to switch between the two chains depending on which chain profits them the most or aligns with their Bitcoin block size limit philosophy.
Upon forking, Bitcoin Cash (BCH) implemented a new feature into its software, Emergency Difficulty Adjustment (EDA), such that in case of losing hashing power (due to miners leaving the BCH chain) it adjusts the difficulty of block time until it regains the lost hashing power.
This is NOT the case for Bitcoin (BTC) as it does not have EDA feature. To have this feature BTC needs to have a hard fork! BTC can adjust the difficulty only after the next block of 2016 multiplier reaches.
Bitcoin Fatal Vulnerability occurs when the block time increases leading to some miners switching chain. As more miners leave, the problem gets worse and a feedback loop results in the dreaded Chain Death Spiral in BTC.
Bitcoin Cash can not die because it has EDA. Bitcoin can die because it doesn’t have EDA. Bitcoin Cash's value can not go to zero. Bitcoin value can go to zero.
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