‘The crowd therefore who were with him when he called Lazarus out of the tomb and raised him from the dead, bore witness. This was why the great crowd also went and met him, because they heard he had done this sign.'
John then connects the enthusiasm of the crowds with the raising of Lazarus. This was one of the main reasons for their enthusiasm. The crowd that had been with Him when he called Lazarus out of the tomb had inevitably testified about what they had seen, and the reason the crowd went to meet Him was that they had heard ‘that He had done this sign'. So the testimony of eyewitnesses was passed on and helped to result in this great welcome of the raiser of the dead.