Why does the false prophet perform miracles in the tribulation?
He performs great wonders, even calling fire from heaven, to deceive the earth's inhabitants and convince the human race that he is the truth. Though a counterfeit, his miracles direct worship to the first beast rather than the God of creation, and his power comes from Satan.
Les explains that the false prophet, a religious leader, will do great wonders, including making fire come down from heaven in the sight of men. His purpose is to use miracles and power to convince the human race of who he is. He is a counterfeit, but he will convince people that he is the truth. In verse 14 he deceives those who dwell on the earth by means of those miracles. Les also ties this to the first beast: the false prophet causes the earth and those who dwell therein to worship the first beast, the Antichrist counterfeit, rather than the God of creation. He will have a great religious organization at his disposal and enough power to draw people under that umbrella into worship of the beast or empire whose deadly wound was healed. Les warns not to forget that Satan has power to perform miracles; Pharaoh's magicians in Egypt did it, others in the Old Testament economy were able to do it, and they will do it again in the tribulation, receiving their power from Satan.