Verses 18-21 speak of the fact that sending Jesus to die on the cross for our sins was always in God's plan. VV 22-25 are about Christians being born again and becoming a new creation.
1 Peter 1:18-25
New King James Version (NKJV)
18 knowing that you were not redeemed with corruptible things, like silver or gold, from your aimless conduct received by tradition from your fathers, 19 but with the precious blood of Christ, as of a lamb without blemish and without spot. 20 He indeed was foreordained before the foundation of the world, but was manifest in these last times for you 21 who through Him believe in God, who raised Him from the dead and gave Him glory, so that your faith and hope are in God.
22 Since you have purified your souls in obeying the truth through the Spirit[a] in sincere love of the brethren, love one another fervently with a pure heart, 23 having been born again, not of corruptible seed but incorruptible, through the word of God which lives and abides forever,[b] 24 because
The Enduring Word
Now this is the word which by the gospel was preached to you.