Sometime last year, I came across the flow chart pictured below. They were so close to the answer, so I decided to give the explanation for the path I circled. Hopefully, this helps someone understand the plan of God.

He did destroy Satan, when Jesus died and when to hell, he destroyed death and the grave, and he made a spectacle of all the demons and their cohorts (Colossians 2:15).
So currently Satan only has power over those who let him have that power. Right now, we still live in this world as is because God is being patient with people (2 Peter 3:9). He doesn’t want them to also be destroyed with Satan, so he’s giving them the opportunity to accept Jesus and be saved (like he gave people the opportunity to get on the arc with Noah before the flood).
God is merciful, he doesn’t want people to perish, but He does not want to force anyone to do his bidding either. He would rather they chose willingly to come to Him. He’s done everything already. It’s up to us to accept What he has done and wait patiently for the day that the new Earth and the new Jerusalem will be revealed for all of God's people to be able to live with God, in a recreated world without sin (Revelations 21:1-4).
So why create evil?
He didn’t create evil. Because God is good, where ever He is not, there is no good. So evil comes from the absence of God in or from something.
When God recreated the Earth, he gave dominion over it to Man (Adam). But Adam allowed Satan to take over that dominion when he listened to him and ate from the tree. At that point, man started hiding from God (because he realized his nakedness). And that separation from God made way for evil. Because without good (God), is evil. Just like without light is darkness.
The earth was void, chaotic, and absent of light until God hovered and brooded over it, and brought light, order, and filled it. (Genesis 1-3)
Did he not anticipate Adam would eat of the Fruit? after all he’s all-knowing.
He did, that’s why he made the plan for the sacrifice of Jesus. The plan for Jesus wasn’t an afterthought, He planned it from the beginning (John 1:1, John 1:10).
Rather than destroy everything and “start over” he decided to let everything play out. He holds all the pieces to the puzzle, and He decides how he wants to solve that puzzle. Does a clay pot ask its potter “Why did you make me”?
What do you think of this explanation? Am I missing anything? Do you have any additional questions? Contact me and let me know.