Kalam always attracted huge crouds. He had a vision and was intellectual. Getting high marks in India doesnt mean much. Big difference between being smart and intellectual.
But as you say, if the PM had gone, he would not have been ignored. Unless the Indian president is well known the position itself is thought to be unimportant relative to PMship and doesnt invite interest. In fact it might be considered disrespectful that India sent a ceremonial head to visit.