After the calamity when computer networks went down, all centralised data was suddenly lost. All that remained was the Bitcoin blockchain that we found copied on all the computers we recovered.
People had recorded their lives in the margins of Bitcoin transactions because they knew the blockchain could not be altered and would likely survive forever. They recorded their prayers and wedding vows, wishes and messages to the future and memorials for the dead.
In the same way as the Domesday book became a record of life in the 11th century, the Doomsday Blockchain is now the only record of life in the 21st century.