I believe it's a question of angle of attack (orientation of the wings vs the direction of airflow). The more you angle the wings, the more upward lift they gen

I believe it's a question of angle of attack (orientation of the wings vs the direction of airflow). The more you angle the wings, the more upward lift they generate. So when the pilots commanded the plane to "rotate" (take off), they had to pull it back farther than expected to generate sufficient lift for the heavier-than-calcuated and slower-than-calculated plane to leave the runway. That means the nose of the plane was pointing higher than normal, which means the tail was lower than normal. (Note that you can't keep increasing AoA indefinitely if you need more lift; at a critical speed, the airflow will separate from the wing and stop generating any lift. That's an aerodynamic stall.)