In Deus Nova, the population is growing exponentially over centuries. In Nihil Morari, the song directly prior to this song, the population is still rapidly growing at intervals of decades between Year 2000 AD and Year 2050 AD.
In this song, a global catastrophe/doomsday event has occured, causing the global population of 10 billion to become reduced to simply 1.2 million, an event known as a "population bottleneck".
Simple: Population bottleneck.
In Deus Nova, the population is growing exponentially over centuries. In Nihil Morari, the song directly prior to this song, the population is still rapidly growing at intervals of decades between Year 2000 AD and Year 2050 AD. In this song, a global catastrophe/doomsday event has occured, causing the global population of 10 billion to become reduced to simply 1.2 million, an event known as a "population bottleneck".
Put short, humanity got pwned. Hard.