Matthew 27:18

‘For he knew that for envy they had delivered him up.'

And the reason that Pilate was so desirous of getting Jesus released was because he was aware of the motives of the Jewish rulers. He recognised that they were acting out of spite and jealousy against Someone of Whom they were afraid because He had continually exposed them, and against Someone Who was more popular than they were. (Constant information would have come back to Pilate about Jesus' activities. With the excitement He aroused among the crowds He was the kind of person Who would have been kept under strict observation). And he knew that if he could but get the crowds on Jesus' side and arrange the release accordingly, using the custom previously referred to, he would be off the hook. However the problem that he had was that he still did not understand the mentality of certain Jews. Nor did he consider the fact that someone being championed by him was unlikely to be chosen. The last thing any of them wanted to do was to please Pilate.