God has revealed his plan to establish an earthly kingdom, that's where the idea comes from.
Over-spiritualising scripture carries as much risk as over-literalising it.
In your example Jesus was talking to Pilate, a man of authority in the kingdom of the world, in this case- Rome.
In this context
"The earth" = the creation which God has told us he will redeem.
"The world" = The fallen worldy system which God has told us he will destroy.
In scripture Satan is called the "the god of this world"
It is equally true that scripture declares "the earth is The Lord's and everything in it."
"Your kindom come, your will be done, ON EARTH as it is in heaven."
Look here;
Acts 1
6 Then they gathered around him and asked him, “Lord, are you at this time going to restore the kingdom to Israel?”
7 He said to them: “It is not for you to know the times or dates the Father has set by his own authority.
Jesus could have corrected them if they were wrong about the coming kingdom.
He did not say there wasn't a kingdom to come, only that it wasn't for us to know times & dates.
Rev 11
15 The seventh angel sounded his trumpet, and there were loud voices in heaven, which said:
“The kingdom of the world has become
the kingdom of our Lord and of his Messiah,
and he will reign for ever and ever.”
Rev 21:3
And I heard a loud voice from the throne saying, “Look! God’s dwelling place is now among the people, and he will dwell with them. They will be his people, and God himself will be with them and be their God.
Matt 25
31 “When the Son of Man comes in his glory, and all the angels with him, then he will sit on his glorious throne. 32 All the nations will be gathered before him, and he will separate them one from another, just as a shepherd separates the sheep from the goats
Mat_6:10 Thy kingdom come. Thy will be done in earth, as it is in heaven.
Rom 14:17
For the kingdom of God is not meat and drink;
but righteousness, and peace, and joy in the Holy Ghost.
Mat_4:17 From that time Jesus began to preach, and to say, Repent: for
the kingdom of heaven is
at hand.
Mar_1:15 And saying, The time is fulfilled, and the
kingdom of God is at hand: repent ye, and believe the gospel.
I don't think He meant for us to seek a earthly throne.
Mat_6:33 But seek ye first the kingdom of God, and his righteousness; and all these things shall be added unto you.
If His kingdom is , yet to be ,how does this verse fit
Mat_11:12 And from the days of John the Baptist until
now the kingdom of heaven suffereth violence, and the violent take it by force.
Did Jesus cast out devils?
Mat_12:28 But if I cast out devils by the Spirit of God, then the kingdom of God is
come unto you.
Luk_17:20 And when he was demanded of the Pharisees, when the kingdom of God should come, he answered them and said, The kingdom of God cometh
not with observation:
Luk_17:21 Neither shall they say, Lo here! or, lo there! for, behold, the
kingdom of God is within you.
Joh_18:36 Jesus answered,
My kingdom is not of this world: if my kingdom were of this world, then would my servants fight, that I should not be delivered to the Jews: but now is my kingdom not from hence.