Bitcoin’s skyrocketing popularity was causing difficulties for the bitcoin mining community, which struggled to keep up with the capacity of transactions. Traders were having to wait an increasingly long time for their transactions to go through, and expected to pay additional fees if they wanted things to move quicker.
Cue disagreement within the community about how exactly to solve the scalability problem. Many miners felt that existing restrictions imposed by the software needed to be revised, while others felt this would disincentivise miners and devalue the cryptocurrency. This ultimately led to a split, or ‘hard fork’, in the blockchain.
Bitcoin forks aren’t uncommon, but there is usually a consensus on which version of the blockchain to discard. On this occasion, however, neither was discarded. This resulted in two tokens: the original bitcoin, and the new bitcoin cash.
This enabled bitcoin cash miners to apply new rules to their mining software and expand the currency’s transaction capacity, among other changes. As such, despite a shared transaction history, the two currencies are now entirely incompatible with one another.