I've read a lot about how Egypt is suffering from the Russian invasion of Ukraine because it imported a majority of its grain from Ukraine. And yet, if you read any ancient historian, they mention Egypt being one of the most fertile places in the west, with its grain exports feeding much of the Mediterranean and making its rulers exceedingly wealthy.
What happened over the past two thousand years that changed Egypt's agricultural productivity? Was it just a massive population increase? Was there a change in the climate of the Nile valley?
This is by no means a complete or final answer, but for starters you might want to check out this answer I wrote on the topic a few weeks back.
Anyway, that's not the entire historic story. I'll note that the Roman era population of Egypt is estimated at around 7 million, and that the population decreased quite a bit in the Medieval period, and did not again reach that level until the late 19th century (and even in 1800 the population was around 2 million). Hopefully a scholar on Medieval Egypt can speak more to that trend, but my understanding is that partially what happened is that population decreases from events like the Black Death caused the elaborate irrigation systems to not be properly maintained, which caused them to malfunction and make farming more difficult, which in turn fed back into population decreases. Very specifically in the past century, Egypt has had huge population growth, combined with economic and political factors that have favored growing animal feed crops over wheat, plus the Egyptian population being extremely heavy wheat consumers by world standards.