I think their Bitcoin payment method is actually to facilitate international payments (funny in a dark way) - they also take the popular shady prepaid-debit/cash-wire service GreenDot Moneypak and I'd imagine most US victims paid up that way.

There are a couple of anecdotes on Reddit about Canadians and other non-US residents scrambling to find a physical Bitcoin storefront or Craigslist contact to pay the ransom for them since Moneypak wasn't available in their area.