John 12:18 KJV
For this cause the people also met him, for that they heard that he had done this miracle.
There had to have been some catalyst for the crowd of people casting palms and calling Jesus King. They had seen miracles they had followed Him and even attempted to force him to become king. This time they just assumed Him as their king. The miracle of calling Lazarus from the grave where he had laid four days was witnessed by so many and spread so quickly and was of such dramatic nature that they took this upon themselves without consultation organization or approval. He would be king.
But the same catalyst for the palm branches was the final straw in the Pharisee's mounting antagonism against Christ. So dramatic a miracle as that could not convince the heart given over to religion. So dramatic a miracle as that could not change the hearts of people who, though calling Christ king, believed only for what they could get.
It is the heart God is after and the heart is only reached through humility and not miracles. We need miracles. They sustain us and give us victory over the obstacles of a world bent in opposition to the Lord. But the cross; that of Christ and our own crosses, are essential to faith. They give us victory over the enemy in our own flesh.