Sometimes yes, sometimes no. Here's a quick list of some successful forks:
- Ubuntu was a fork of Debian
- LibreOffice was a fork of OpenOffice
- Webkit was a fork of KHTML
- KompoZer was a fork of NVU
- Wordpress was a fork of b2/CafeLog
- Zen Cart was a fork of osCommerce
- TrueCrypt was a fork of E4M
- Inkscape was a fork of Sodipodi
Obviously some of these forks are pretty well known.
There are plenty of projects that went on to be successful after being forked. As for reasons why--they tend to vary: project mismanagement, a project going dormant, changes in direction/focus, technical limitations, or changes in the scope from the original project.
an unrelated note, here's a blog post that offers a more direct and better explanation of the reasons for the Blink fork: http://infrequently.org/2013/04/probably-wrong/