They thought they'd wiped out smallpox. No naturally occurring cases since 1977.
No companies have been producing smallpox vaccines for years, no money in it. It'll take a while to get 300,000,00 doses.
They thought wrong, didn't they. That's what we get for trusting the WHO. It seems to me that smallpox has been such a scourge of humanity for so many thousands of years that we might have kept the vaccinations going for a bit of an "overlap" period. Would that have been unreasonable?