"'And besides, he has brought Greeks into the temple area and defiled this holy place.' (They had previously seen Trophimus the Ephesian in the city with Paul and assumed that Paul had brought him into the temple area.)" NIV translation
One charge was not enough for them so they came up with another which was defiling the temple by bringing someone who was unclean (a Gentile) in. Nobody saw Trophimus in the temple but they didn't let the facts get in their way. Gossip and rumors were a destructive force back then and they are as well today. In James 3, we are warned about this destructive force. The good news is that this gossip will be used by God to spread the gospel.
"The whole city was aroused, and the people came running from all directions. Seizing Paul, they dragged him from the temple, and immediately the gates were shut." NIV translation
We see that the gossip and rumors that started with a small group has got the whole city going. Nobody has stopped to ask whether the charges are true or not but now you have a mob.
This calls to mind the words of Jesus and the six woes mentioned in Luke 11:37-53. The last woe was where He said that the experts of the law were hindering the gospel.
"While they were trying to kill him, news reached the commander of the Roman troops that the whole city of Jerusalem was in an uproar. He at once took some officers and soldiers and ran down to the crowd. When the rioters saw the commander and his soldiers, they stopped beating Paul." NIV translation
The people of God were the ones that were trying to kill Paul but God intervened and sent the Romans to protect his life. The same type of thing happens today as too many Christians are fighting other Christians instead of resisting the devil.
"The commander came up and arrested him and ordered him to be bound with two chains. Then he asked who he was and what he had done. Some in the crowd shouted one thing and some another, and since the commander could not get at the truth because of the uproar, he ordered that Paul be taken into the barracks." NIV translation
Those that were making accusations against Paul couldn't even get the story straight. Even so, Paul did not resist but still kept his eyes on the fact that God is in control. This is a good example of what God would have us to do in the face of persecution.