God’s motivation and his purposes are really quite understandable, and purpose for our lives is also involved in his. One of God’s purposes is to increase and share his joy – he is happy in himself.* He is a good Father, and one of the ways of increasing his joy is by enlarging his family. He gets joy for himself in our pride in him as our Father, and in our joy in reciprocated familial love. Notice that we get joy, too.
God intended two creations from the start.** Without death and evil in his first creation, we could not understand and fully love him for his justice, mercy, grace and love to us through the Lord, Jesus, the Christ. Jesus’ motivation is also explicit and clear, and it was forward looking***: “for the joy that was set before him endured the cross, despising the shame.” Hebrews 12:2. That joy is us(!), if you are a Christian.
The New Earth will be perfect, and without evil.
*See The Pleasures of God: Meditations on God's Delight in Being God - Kindle edition by John Piper. Religion & Spirituality Kindle eBooks @ Amazon.com.
**"Then the King will say to those on his right, ‘Come, you who are blessed by my Father, inherit the kingdom prepared for you from the foundation of the world." Matthew 25:34
***Our motivation should be forward looking, too, toward future grace. Future Grace, Revised Edition: The Purifying Power of the Promises of God - Kindle edition by John Piper. Religion & Spirituality Kindle eBooks @ Amazon.com.