Since God changed His Law, then apparently God changes His mind a lot.
Actually God planned the change all along. The Law of Moses defined sin and bound it to mankind, but it could not in itself save. It spoke only of future salvation. "For the law made nothing perfect; on the other hand, there is the bringing in of a better hope, through which we draw near to God" (Hebrews 7:19). Salvation came by Jesus as the Law of Moses foretold.
"Knowing that you were not redeemed with corruptible things, like silver or gold, from your aimless conduct received by tradition from your fathers, but with the precious blood of Christ, as of a lamb without blemish and without spot. He indeed was foreordained before the foundation of the world, but was manifest in these last times for you" ( I Peter 1:18-20).
"Therefore do not be ashamed of the testimony of our Lord, nor of me His prisoner, but share with me in the sufferings for the gospel according to the power of God, who has saved us and called us with a holy calling, not according to our works, but according to His own purpose and grace which was given to us in Christ Jesus before time began, but has now been revealed by the appearing of our Savior Jesus Christ, who has abolished death and brought life and immortality to light through the gospel" (II Timothy 1:8-10).
Many people plan to retire one day. The fact that they do does not mean they changed their minds about working. They began their careers with the knowledge that it led to a goal.