“For there is one God and one mediator between God and humanity, the man Christ Jesus, who gave Himself as a ransom for all people.” (1 Timothy 2:5-6)
Ransom is defined in the Merriam-Webster dictionary as “a consideration paid or demanded for the release of someone from captivity”. A ransom is not a debt that is paid, it is a payment required for release of a captive. So what was “demanded” of Christ Jesus? Not money or any material thing. The demand for the release of "all people" was His LIFE.
But who did He pay? Who or what was holding humanity captive?
God gave His Son to "ransom" humanity from its captor, death so that it can be abolished...
“You are the Christ, the Son of the living God. Jesus replied, Blessed are you, Simon son of Jonah, for this was not revealed to you by flesh and blood, but by my Father in heaven. And I tell you that...on this rock I will build my church, and the gates of Hades [the grave] will not overcome it...As in Adam all die, even so in Christ shall all be made alive...the last enemy that will be abolished is death.” (Matthew 16:16-18; 1 Corinthians 15:22-26)
Again, the LIFE of Jesus was the ransom paid to DEATH to free its “captives”. God assures us that death’s “prisoners” will have “freedom” from death when they are "made alive".
“The Spirit of the Sovereign LORD is on me, because the LORD has anointed me to proclaim good news to the poor. He has sent me to bind up the brokenhearted, to proclaim freedom for the captives and release from darkness for the prisoners” (Isaiah 61:1)
Paul was probably thinking of "freedom" from the "captivity" of death when he wrote…
“Therefore I, the prisoner of the Lord, implore you to walk in a manner worthy of the calling with which you have been called…there is one body and one Spirit, just as also you were called in one hope of your calling; one Lord, one faith, one baptism, one God and Father of ALL who is over all and through all and in all. But to each one of us grace was given according to the measure of Christ’s gift. Therefore it says, when he ascended on high he led captivity (death) captive and He gave gifts to humanity (eternal life).” (Ephesians 4:1-8)