Charles Spurgeon Commentary Acts 8:7-11

"For [from] many of those that had unclean spirits, they came out, crying with a loud voice: and many that were palsied, and that were lame, were healed. And there was much joy in that city. But there was a certain man, Simon by name, who beforetime in the city used sorcery, and amazed the people of Samaria, giving out that himself was some great one: to whom they all gave heed, from the least to the greatest, saying, This man is that power of God which is called Great. And they gave heed to him, because that of long time he had amazed them with his sorceries." — Acts 8:7-11 (ASV)

For unclean spirits, crying with loud voice, came out of many that were possessed with them: and many taken with palsies, and that were lame, were healed. And there was great joy in that city.

But there was a certain man, called Simon, which beforetime in the same city used sorcery, and bewitched the people of Samaria, giving out that himself was some great one: to whom they all gave heed, from the least to the greatest, saying, This man is the great power of God. And to him they had regard, because that of long time he bewitched them with sorceries.

He had managed to secure great influence over the people, and he held them under his wicked rule.