Go straight to the source. To find out what was in the mind of the customer, you need to interview the customer.
Don’t rely on sales reps to tell you why they won or lost. Sales reps are not mind readers! You should still survey reps, but ask them questions they can answer:
- Which competitors were they up against?
- Who won?
- What aspects of the campaign went well or not well?
- Were there any surprises?
- Any best practices to share?
- Any feedback for corporate?
These kinds of insights complement what you learn from customers without inviting speculation.