People realized there was power of evil when there was world war and when planes were driven into the twin towers and other places to kill many people in 2001. There is the ongoing mind that continues to bring evil to this creation from God with us in it.
Satan was not spoken of by Jesus as much as hell was. The real threat to humanity is not coming to God as made possible through Christ and his work and atonement for us and going to hell then. Satan is working to keep people from coming to God in that way and have them perish. He is the god of this world, as he is called, and is as powerful as gods that people believe in are, but not at all so powerful to be competition to God the Almighty who has no limit, but Satan does not appear to people in direct visibility and won't until the world is ready for it, which it is being brought to very soon as God is dismissed by people generally. Until then it works better for Satan's efforts if he is dismissed as well. He is the accuser of people in this world, he is also the deceiver and the tempter, to have people led to sin, wickedness, and destructiveness effectively. Just through Christ to come to God is there escape from this. When we are in Christ with the relationship and love in how we live, we won't be subject to Satan's work in our lives, so we should continue that in Christ.
There is real evil, with sin, wickedness, and destructiveness from this real influence that is on far greater scale than almost any recognize, but can be seen with a real look at powerful players, large businesses and state governments in this world, from this real influence that could be recognized.