simply because they felt good doing it, the devil got into them.They thought that by doing it, they could get revenge. They want to prove to people that Jesus is not superior, not the Son of God. They don't wanna accept the fact that Jesus could do such amazing miracles because they wanna be the boss.They don't want anyone be bigger,stronger and more powerful than them. They got alarmed hearing people worshipping Him. Jesus is a threat to them. They hurt and mocked Him because they wanna wake the people up that Jesus' miracles aren't real and it's not even helping Him. They wana tell His believers and followers that "hey! this is what you call the Son of God? He could not even help Himself right now, Look, how helples He is! If he is the Son of God, let's see how He could get His way out of here and avoid this torture or let the sky fall down on us  who are torturing Him or maybe let the thunder kill  us!" 

They didn't know the essence of everything Jesus did, they thought that by doing that they won, conquer and overcome the world but it's Jesus who got it!