Satan set up his kingdom by fraud and usurpation, and he maintains it by force. Those are his characteristics. But God is love. His kingdom is founded upon love, and the only power He uses in His kingdom, is the power of love.
The charge Satan brought against God was that He was arbitrary, determined to have His own way, and did not love His people. He promised, if the angels would follow him, to set up a better kingdom. Now it remains for this pledge to work out. While God can see the end from the beginning, created beings cannot.
Had He at the first crushed out the rebellion by force; had He suppressed it by mere force, there would still have been in the minds of created beings a question of God's justice. So God lets Satan work out his plan, that all the universe may see the contrast between Satan's plan and God's plan. And . . .