With 5 billion dead that would leave a population of 3 billion, the same as when I was a kid. Wholesale genocide of WWII had only just stopped. Perhaps 3 billion people were too many. One million could not support a global civilization so what number of humans would be stable? Billionaire tribal chiefs would have lost their status and power. Farming communities might make a go of it depending on raiding party threats and climate. As for Jesus, he was a no-show.