In a book about Adeniums, there are photos of a species that grow sprawling down cliffs from the caudex--- Yemen or someplace like that ( I need to go back and learn that one!)
Some simply do not grow up no matter what. Some grow to the sky no matter what, the tall ones. I have one that didn't bloom until it was three feet tall, then it got one branch, and bloomed again when it was five feet tall. Now it's rather like a tree. Siam Adenium, a huge grower, has a variety called "Anaconda" that gets ten to twelve feet tall!