Cryptocurrency markets have deflated over the past four months. Bitcoin, the granddaddy of the digital-currency industry, has shed more than half of its value. That in itself has caused significant problems, such as the probable default of El Salvador, a nation whose leader unwisely tethered its currency to bitcoin. But key pieces of the ecosystem, such as the TerraUST/Luna “stablecoin,” have it even worse. TerraUST/Luna unraveled entirely, dropping to near zero from $60 billion in total nominal value.