Why did God the Son take the scroll and agree to pay off the mortgage?
God the Son took the scroll because He alone qualified through His work at Calvary: He was slain and redeemed people to God by His blood. As the capable, willing next of kin, He agreed to pay the mortgage in order to lift the curse and deliver the planet.
Les explains that John wept because there was no one in heaven or on earth who could pay off this awful mortgage. An elder told him to weep not, because the lion of the tribe of Judah, the root of David, had prevailed to open the book and loose its seven seals. John then beheld the Lamb—the Christ, the Son God had sent forth. God the Son qualified now because of what He accomplished at Calvary, and He came and took the scroll out of the right hand of Him who sat upon the throne. The heavenly host sang that He was worthy to take the scroll and open its seals, for He was slain and had redeemed us to God by His blood out of every kindred, tongue, people, and nation, making them kings and priests who shall reign on the earth. So God the Son takes this mortgage and agrees to pay it off in order to lift the planet, or deliver the planet of the curse. Les says this goes back to Israeli history of redeeming and gaining back title to what had almost been lost by default; it had to be a next of kin who was capable, had what it took, and was willing.
And he came and took the book out of the right hand of him that sat upon the throne.