The fact that I was selected for an interview means I highlighted many key points. The added fact that the interview was easy was due to familiarity in the applicated field. In other words, I knew and researched valued characteristics and skills for the referred position, notated that we shared common values, and according to the interviewer "That's what we need in this company". Unfortunately, I was denied the position. Possibly, another candidate accommodated more of what the company needed, opposed to me "missing many key points". Thanks for the feedback.

The fact that you thought the interview was easy means that you missed many key points. AT&T hires 1% of applicants so you were competing with probably 10 other people for that slot and many didn't even get called for an interview.