David had an old website with posts dating back 13 years that needed to be preserved. There were a few requirements around the tag clouds, and the new system had to support David's podcasts, but overall the requirements for this site were quite reasonable.
Backdrop was chosen because the new website needed to have all the same features as the old one. Because Backdrop is so similar to Drupal, that was easiest to achieve by keeping the platform nearly the same. Several Drupal modules were ported to Backdrop for this project, but many of the features David needed were already provided by Backdrop core.