It's really simple. For this present world, God has given majority control of it over to Satan. Some may have a difficult time understanding that since they prefer to live in their own mind instead of facing reality, but this is also what God's Word reveals (Luke 4 with what Satan offered our Lord Jesus if He would follow him).
This present world was never... intended to be a replacement for God's future Kingdom to come under His Son, even as our Lord Jesus declared that this world is not His Kingdom, otherwise His servants would fight.
This world and everything in it involving flesh man is designed to perish, not live eternal. Even our flesh bodies are destined to perish. According to Apostle Paul in Romans 8, God placed the present creation in a state of vanity, in bondage to corruption, and by that showing that state cannot be compared to the future glory to come.
So for this present world, Satan and his children have been given advantage. This is why God's people are only able to overcome this world through His help, as we cannot defeat the devil and this world without Him and His Son. This especially means that brethren who think they can create a heaven here on earth in this present world need to re-calibrate their thinking and get in line with what God's Word reveals about it. What He revealed in His Word is a coming destruction by fire of this present world and all of man's works in it (2 Peter 3).