@lee99 - Thanks for raising this issue. We have fixed the problem that was preventing Paragraphs from showing up in the module search on BackdropCMS.org. Please, check again.
In terms of the list of the top 100 modules. As great as paragraphs is, I don't think it is one of the top 100 modules for Drupal 7. Or if it is today, I don't think it was when we created that list about 7 years ago.
In addition to our own inability to keep that list up to date, the actual list of the top 100 modules for Drupal 7 is probably changing all the time as the number of Drupal 7 sites changes, if only slightly.
As of today, Paragraphs is the 10th most popular project (module/theme/layout/core) for Backdrop CMS out of 763 total projects tracked and it is fully supported by the Backdrop community.