Argenti

By making it his mission to kill God, to the point of acquiring a weapon and smuggling it to the Pearly Gates, Grover shows disdain to the concept of divinity and has already killed Him on his mind.
By steeling himself enough to go up the Stairway to Heaven not once, but SEVERAL times, no matter how infinitely great or infinitesimally small were the steps he had to take, and ending it by making Kermit take the entire brunt of his sins, Grover has outwilled God.
By defying the all-binding, all-blinding light of He Who Comes From Above with the sheer strength of his purpose, demanding that He showed Himself before him, Grover had defeated God -- The very concept of God purpose-wise.
Three times had he killed The Father, both in mind, body and spirit. All without firing a single bullet. He had already shown that The Holy Trinity was below him, but Grover still groveled on his spite and foolishness to prove a point, that he would kill God by means as mundane and low as the treason of His own children. The rejection of the gift of Life, the sin against brethren and the audacity to challenge His judgement of life and death: A single tool of murder, the Glock.
Little did Grover know, however, that God has already shown enough mercy. As He once did with Lucifer, his rebellious legion of angels and with several iterations of Mankind, He'd reciprocate his wicked, unfathomable purpose. And so, God broke Grover beyond what anyone would expect.
He broke Grover's purpose by putting the Damocles above his head, "rewarding" him with power over everything and promptly letting it crush his murderous intent. He broke Grover's body by weighing his mortality against the infinity of the sins of His creation on an endless, relentless flight of stairs. Finally, He broke Grover's mind by making him experience his insignificance when compared to the entire span of Creation, so that when Time and Space have no more meaning than a speck of dust, his mortal brain would wither.
Three times had He killed The Muppet by condemning him to sempiternal Death, unending Failure and overwhelming Oblivion. Grover would forever experience everyone's pains and sins, the existence and decay of everything, and everywhere and everywhen that which has been, that is and forever will be. This was God's will. This was Grover's ultimate fall.
~Sebastián Rebaza La Rosa