why is it necessary for us to cooperate in making God's Kingdom fully realized?

It's necessary because of what Jesus said in the sermon on the Mount - especially the bit called 'The Beatitudes'.
He addressed people who were already in the covenant God had made for a kingdom, the earthly kingdom of Israel. At the start of chapter 5, Matthew's gospel, Jesus woke them up to the reality of what it meant to be an active, faithful participant in the kingdom of God. He was counteracting centuries of religious teaching that tried to prevent the ordinary people from enjoying the blessedness of being in God's kingdom. Jesus challenged them to live as subjects of that heavenly kingdom, even if they were mourning or being persecuted because of righteousness.

He exhorted them to have faith in God and in being in His kingdom, "Rejoice and be glad, because great is your reward in heaven, for in the same way they persecuted the prophets who were before you. You are the salt of the earth... You are the light of the world... Let your light shine before men, that they may see your good deeds and praise your Father in heaven."

Likewise with those who have been brought, by Jesus, into the new covenant; "This cup is the new covenant in my blood, which is poured out for you... And I confer on you a kingdom" - Luke 22:20-30. Like the earthly nation of Israel being set apart by God to be a holy nation and a royal priesthood, so Christians must be seen to be ambassadors of God and His kingdom - they must be salt and light in a sin-rotting and spiritually dark society.

We co-operate with God in the blessings of His kingdom by living openly as subjects of that kingdom - pointing to Christ as the King of that kingdom, urging people to be reconciled to God - 2 Corinthians 5:14-21. What is the point in enjoying the blessings of being a subject of God's kingdom if others cannot see that in us?

because Satan's forces cooperate to destroy God's kingdom

We have an enemy (satan), who knows that his time is short, and he is working unabated to sow division among the churches and to distort the Truth. Therefore, it is imperative that we stand firm in the faith; that we will be more willing than ever to free our fellow man from his clutches.

One must keep in mind that Jesus Christ is not going to return to a scattered bunch of churches. Jesus Christ will have only one Bride -- made up of all the brethren who are being led by God’s Holy Spirit.

Since Allah said so. :)

what is God's Kingdom do you mean?

It isn't. You're already doing it whether you like it or not.

Christian's jumped at the chance for this! As now we have classes of people, in the New Kingdom coming is also classes of blessed, not so much blessed. Power, authority to rule is given to the most trusted and faithful. As our lower class sees how the upper class lives here, will be the same also. Ok who here wants to be 3rd. Class? Who here wants to go First Class? I do I do!!!

Why do you assume it is? That's an assumption not based on facts. There most likely isn't any kind of god's kingdom, so cooperation in making one is irrelevant.

Its because the deluded seek out other deluded, you people don't do well with normal people.

You can't see something that's not there. Unless you're hallucinating.

It isn't.

It is however necessary to base our response to the human condition on reality and not absurd nonsense.

Only if you don't want to end up in Hell .

Because there is no hope, on humans

It's been 6000+ yrs

6041 since Adam

Actually 5,939 yrs of human rule

Christ has been ruling for 102 yrs now