Final answer:
The gold standard collapsed because countries abandoned it and adopted fiat currencies, as well as unequal amounts of gold causing instability in exchange rates.
Step-by-step explanation:
The gold standard collapsed because countries abandoned the gold standard and adopted fiat currencies. This shift allowed governments to have more control over their currencies, as they were no longer tied to the value of gold. Additionally, the gold standard became unsustainable due to the unequal amount of gold in each currency, leading to instability in exchange rates.