1. Both are (or were) ennormously popular.
2. They both are known for portability. Although you couldn't keep a Brownie in your pocket it could be easily carried around...especially if you compare it to the view cameras that it replaced.
3. They are both very simple to use. You took a picture with a Brownie by looking down into the finder and clicking a button.
4. They both became the de facto leader in the field. Apple dominates just as Kodak did.
5. Simplicity defines both cameras.