It's just a natural evolution. You start by making handbags, then move into something related.
Kooba, the handbag that I could never figure out, went a little extreme by going to leather jackets. Botkier has taken what seems a more traditional path, and after providing us with all kinds of pretty bags, has shoes. The strange thing is, it's difficult for me to "see the Botkier," in the shoes, if you know what I mean. They don't really have any Botkier signature features and the horseshoe on the sandal in the far right pictured above actually makes the shoe look like it could be by Ferragamo or Gucci.
The shoes aren't cheap. At Shopbop, the thong-style sandal is $225.