John 12:18

For this cause also the multitude went and met him, for they had heard that he had done this sign.

It was the raising of the dead that triggered the appearance of such a large and enthusiastic multitude; and the people who had seen it were telling the story to all whom they met. The popular frenzy at the thought of seeing one who could do such a thing increased as Jesus approached Jerusalem, an immense throng being caught up and swept along by the momentum of such a demonstration.