Perhaps they had no issue with him at all. Perhaps there were simply others whom they felt more suited to the job. Or perhaps they had an ample number of very well qualified applicants, and only so many jobs positions to fill.

It is possible to have a room full of excellent candidates, and not have enough openings for all of them.

Someone not being hired isn't an indictment on the applicant, or the employer. It may simply mean that they didn't get hired, no fault of their own, and no slight upon the employer to which they applied.