The earth hasn't belonged to God. So Christ
has to take back legal possession of it.

God created the world and it belonged to
Him but He then gave legal stewardship or
dominion of it to Adam:

" And God said, Let us make man in our
image, after our likeness: and let them have
dominion over the fish of the sea, and over
the fowl of the air, and over the cattle, and
over all the earth, and over every creeping
thing that creepeth upon the earth.
So God created man in his own image, in
the image of God created he him; male
and female created he them.
And God blessed them, and God said unto
them, Be fruitful, and multiply, and
replenish the earth, and subdue it: and
have dominion over the fish of the sea,
and over the fowl of the air, and over every
living thing that moveth upon the earth.
Genesis 1:26-28