Yes, that was before we manufactured fertilizer. If that invention didn't exist, this number absolutely wouldn't be sustainable.
Soil is now becoming depleted and fertilizer isn't enough.[1] Globally, much also depends on rapidly depleting ground water that isn't being replenished. Agriculture is exceeding its limits.
Humans thought they'd find a fix for their problems before, so nothing to worry about.
A lot of those people died because no fix was found in their lifetimes. Nobody fixed the plagues that went around Europe. Nobody fixed the droughts that killed millions. Entire civilizations went extinct because they weren't able to find a fix before a problem caught up with them.
A lot of problems won't have a fix within our lifetime. Thinking it's guaranteed to happen is magical thinking--assuming we're the main characters in the universe and things must work out. Most of the time, they don't.
The current fertiliser shortages might undo some of that, there's a real chance we see severe famines in Lebanon, Egypt, Sri Lanka, Yemen, and other countries next year.
Soil is now becoming depleted and fertilizer isn't enough.[1] Globally, much also depends on rapidly depleting ground water that isn't being replenished. Agriculture is exceeding its limits.
[1] https://www.nationalgeographic.co.uk/environment-and-conserv...