You have not been asking the right questions.

Business Development & Salespeople belong to a different Professional Breed hence the approach when hiring them should not strictly conform to hiring practices applied to most other professionals ( with all due respect to HR Pros).

This is why during an interview I would recommend, especially if you are hiring on behalf of a Startup, asking them all or some of the below simple questions :

What is your roadmap to helping us achieve our goals?

Can you help us exceed them?