Mark 11:15 So they came to Jerusalem. Then Jesus went into the temple and began to drive out those who bought and sold in the temple, and overturned the tables of the money changers and the seats of those who sold doves.
What would you do if you had set aside a place for little children to play in and a crowd of adults came to drink and party there instead? Would you allow them to carry on whilst children were trying to look for a safe place to play or would you stop and get them to leave?
The temple was set aside as a place where people should have been able to come to worship God at without the world bullying its way in. Jesus was quite rightly upset with the local people for what they had done.