Bitcoin (BTC) worked perfectly as currency in the beginning, until Blockstream took over the development team, and they decided to keep the temporary anti-spam 1MB block limit, making 0-confirmation transactions (instant payments) very risky by implementing return-by-fee (which make transactions reversible before getting confirmed), etc.
Miners mine whatever is most profitable for them, regardless of how good or bad is that cryptocurrency, and they switch between BTC, BCH or any other SHA256 (not Bitcoin Gold, which uses a different hash function) even many times in a given day.
