Why sales hiring goes wrong more often than other hiring
Sales interviews select for the skill being demonstrated in the room. A candidate who is warm, quick, and persuasive in conversation is displaying exactly the competency an interview measures well, and it is often not the competency the job requires most. In the majority of small-company sales roles, the daily work is disciplined follow-up, accurate qualification, and the willingness to have a slightly awkward conversation about budget. None of those show up in a pleasant forty-five minutes.
The second reason is that expectations are usually set by arithmetic that cannot work. A business with a four-month sales cycle hires someone in January and is disappointed by March. Nothing that person could have done would have produced revenue in that window, but the disappointment is real and it shapes how they are treated for the rest of their tenure.
Both problems have the same remedy: decide in advance what you are looking for, test for it rather than talk about it, and derive the ramp from your own cycle rather than from impatience.
