I think today’s Mass readings shed some light on this issue.
In Wisdom 2:23-24 it says,
“For God formed us to be imperishable; the image of his own nature he made us. But by the envy of the devil, death entered the world, and they who are allied with him experience it.”
The devil envied God.
the devil was envious of man also
from
newtheologicalmovement.blogspot.com/2010/04/why-did-devil-fall.html
What could he have been envious of in man though? Man is, after all, lower in terms of natural capacity than the angels. Angels are pure spirit, they have an intellect a matter of magnitude more powerful than our own and besides all of this they were created before man, “God created the heavens and the earth.” (Genesis 1:1) Back to the initial question, “What was the Devil specifically envious of in man?” I believe the Devil was envious of the glory to which Jesus Christ would raise man through His passion, death, resurrection and glorious assumption. Ambroggio Catarino, a fourteenth century Dominican commentator on Saint Thomas Aquinas, taught that the Devil fell not only because of pride but also on account of envy when God revealed to him the mystery of His will (C.f. Ephesians 3:9); namely that God would become a man and not an angel and by means of this becoming man, He would raise man to glory, a glory higher than the angels. Satan, Ambroggio Catarino reports, went insanely mad upon receiving this revelation of God’s plan, so much so that He rebelled and hated Jesus Christ and thus all men. “For by His incarnation the Son of God has united Himself in some fashion with every man.” (Gaudium et Spes, 22) The deep hatred the Evil One bears toward Jesus Christ also explains why Satan hates priests so much; the priest extends the saving mission of Jesus Christ through time and space by acting in persona Christi capitis (in the person of Christ the head) when celebrating the Sacraments, especially the Holy Eucharist.
Finally, I must say that Ambroggio Catarino’s interpretation of the Devil’s fall is by no means binding on Catholics and for that matter it should be said that there is theological debate concerning whether or not the second Person of the Blessed Trinity would have become man, had man not sinned. I hold that even if man had not sinned in the Garden of Eden, the Person of the Word would still have become man as Glorificator (Glorifyer). Obviously, because the sin of Adam actually took place in history, the Word became flesh to “save his people from their sins” (Redemptor) but, nevertheless, He still glorifies us (Glorificator) by sending the Holy Spirit into our hearts, so that we might become sharers in the divine nature. (2 Peter 1:4) Jesus is our redeemer and our glorifyer and for this the Devil hates Him and is envious of us with a hatred that frightens to the core.
Let us listen to the beautiful words of Pope Saint Leo the Great in response to the question, “Why did God not prevent the first man from sinning?” “Christ’s inexpressible grace gave us blessings better than those the demon’s envy had taken away.”