I wonder why human beings are so important in the conflict between the fallen angels (demons) and Jehovah

I'm not an expert by any means, but my understanding is that humans are God's special children because we supposedly have the choice to believe in him or not (I don't accept that faith is a matter of free will, but that's the theory). The angels in contrast have direct knowledge of God and have no free will in this area. So humans are a prize to be fought over; if the demons manage to convince us to not believe, they've won the contest.

In the garden of Eden Satan actually speaking words of truth manipulated Eve because of her desires to be as God herself, into eating the fruit of the tree of knowledge, Satan was already in his fallen state.

Jesus said he beheld Satan is lightning fall from heaven.
https://www.biblegateway.com/passage/?search=Luke%2010%3A18&version=KJV

Paul says the ruler of this world has been judged, speaking of Satan. That is telling us that Satan is the only one of all of the Angels that were cast down from heaven to Earth. He is the only one that has been judged, judgment is pending on all others.
https://www.biblegateway.com/verse/en/John%2016%3A11

The Old Testament refers to the Lord as the Lord of hosts, host meaning an army, multitudes of angels. And he is mighty in battle, which means he has fought a battle or battles https://biblehub.com/psalms/24-8.htm

https://biblehub.com/exodus/15-3.htm

Ministers teach that Satan is jealous because God loves us. That Satan wants to destroy anything that God loves, and those who try to serve God who are his targets. And when you look at life man himself man has a tendency to be jealous of other humans for various reasons, some to the point that they will do anything to discredit or destroy.

Suppose Satan's unquestionable anger and hatred of man is because he knows who our spirits truly are. Anger because we're given away to redemption and he wasn't, but he has been condemned carrying out of sentencing. Suppose the spirits within us are actually the spirits of those angels that were cast out of heaven down the Earth with Satan. Why haven't those angels, the 1/3 that were cast out of heaven with Satan been judged, the Bible does not speak of them. And 1/3 of the innumerable host of angels that's a lot that man cannot put a number to.

Humans are already have the nature to sin by being disobedient to God, Satan just uses it, some call it tempting.

Used to be and the older Bibles that once this is over, in the new heaven and new earth, there will be no more redemption, if anyone even thinks wrong they will be immediately destroyed. They have removed and are changed a lot of scriptures in these free translations.

Because God wanted to use demonstration to show why He is and can only be God and why lucifer and angels cannot be gods equal to Him...

God created a stage where the contraversy could be played out and humans play a central role in this staged production... lucifer / satan as it where took the bait and attempted and succeded in sabotarging Gods creation, But God already foreknew what satan was going to do and in effect gave satan enough rope to hang himself.. God allows satan to demonstrate to the heavenly host exactly why he is unworthy of Godhood and at the same time by Redeeming His creation God revels why He is the one and only awesome God of perfect wisdom..

God has already won the debate, His universe production has already revealed the truth.. all that is left now is time for those who are destined to eternal existence in Gods perfect eternal existence to chose His Way and for those who want to chose to be eternal losers to chose to follow satan into the eternal lake of fire..

Reads just like mythology.

God could have killed off Satan long ago……. But, he didn’t. Just goes to show, the world needs villains. To keep it interesting.