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?
If yes. How?
How will you help us develop our business from scratch?
How will you generate leads for our brand?
How are you going to turn those leads into New Partnerships/ Revenue?
How will you Sell / Communicate our brand ?
Can you identify the SP's or USP's of our product / brand / service ?
How will you ensure Repeat Business / Sales?
I am sure many interviewees will feel uncomfortable with this approach but on the other hand, you will maximize your chances of hiring the " Right" Candidate simply because you will be making your choice based on answers to everyday business challenges rather than candidates' " glorious" track record on previous positions alone.
Remember : Businesses do not fail. People do. Startups do not fail. Founders do.
Sales is not just another link in your business chain. It is THE link that keeps your business engine running.
Go beyond the obvious , the easy and convenient, differentiate, be unique and creative in your approach, if your product is not groundbreaking, and new amazing growth opportunities will unfold before your very eyes.
Work with experts able to create new business paths and not with people that simply fit a job description. Especially if your business is a Startup.
Understand and embrace basic human business and marketing principles and your business will grow and flourish.