1. You gave off a strong vibe that said: “We’re doing you a favor.” The line between professional pride and arrogance can be a fine one to walk. It’s important to tell a candidate all about your team’s successes and strengths. But in the course of even the most well-earned self-praise, perhaps you and your colleagues neglected to add a very important element to the conversation: “And here’s how we think you will make us better.” 
2. The hiring process sent bad signals. Was it well-organized? Were the interviewers welcoming, even if they asked tough questions? Or did the candidate lurch from person to person, some of whom seemed unprepared or unenthused? Even worse, did any of them diss their colleagues or dump on the organization during the conversations? You can imagine a candidate saying, “If it’s like this when they’re hiring, what’s the culture like the rest of the time?”
3. Your employees weren’t your recruiting partners. It’s a great feeling when you can confidently encourage a candidate to chat up current and former employees for the real scoop on your shop. It shows you value staff participation and trust that even the worst thing they might say won’t scare someone off. Face it, applicants will find a way to get info from people who have experience with you and your organization. What are they learning?
4. You’re a market laggard — and it showed. People go to work for underdog organizations all the time — for the right reasons. It may be less-than-first tier (in size, ratings, circulation, engagement, or awards) but if the outfit is scrappy, its team seems happy and there’s a clear mission and vision, people opt in. They may enjoy being part of something challenging and innovative — pushing against the status quo. But if those elements are lacking, there’s no strategy for improvement and growth, and the place seems mired in mediocrity, they opt out.
5. Inclusivity seemed more than iffy. Candidates are acutely aware when there are few (or no) others in the organization who look like them. They are understandably wary about the absence of people whose backgrounds or expertise, including at the top level of leadership, resemble theirs. Or when hiring conversations reference gender, ethnicity, race or social issues in ways that raise doubts about whether the candidates could (or would want to) feel they belong there. Red flags also fly when candidates are told they are being hired to “lead change” but sense that the organization lacks the resolve and resources to make that hard work a reality. No one wants to be “set up to fail” by their employer.
6. You left too many questions unanswered. Hiring managers shouldn’t make promises they can’t keep. But candidates want to know about career advancement, training opportunities, how evaluations are done, how raises are determined, how tools and technology are allocated to staff and what changes might be in the works. If the answers they get are too vague, they may turn you down.
7. You’re just fine, but your company isn’t. This is a heartbreaker. You can be a first class manager, leading a solid team, but your company has developed a reputation that overshadows your work. Insolvency. Instability. Bad employee relations. High profile scandal. All of those make it harder for you to close the deal with a great candidate — and easier for them to say “yes” to a competing offer from a place with less baggage.