1. Drupal is based on PHP, mysql and CSS - three technologies I'm which are already familiar with.
2. www.whitehouse.gov recently chose Drupal. I'm going to assume that means that their experts believe that Drupal is secure and scaleable. I know this is lazy thinking; it could also mean that it will take a team of hundreds to keep Drupal secure and scaleable, but I'll test that out!
3. The Drupal ecosystem is so active that even the themes and modules have variations and plugins.
4. The Drupal sites I looked up look both attractive - and somewhat similar to each other. This suggests to me that the developers are able to get a lot out of the basics.
5. Adding my own applications to Drupal looks reasonably easy.
