If I knew, believe me, I wouldn't shut up about it. It happened suddenly and only seemed to effect Earth. My father was an astronaut and survived, basically saved humanity. Turning us back was sheer luck. A special chemical compound dripped on the stone surface that encased us and then we became human again, alive and in tact. Not everyone, sadly.
We were frozen in stone for thousands of years. Landscape shifted and changed, buildings disintegrated, you get it. Not everyone was able to stay together. We all do what we must and often have to make decisions some of which we may regret later. It is what it is and can't change the past.