Of course it was not impossible for God to atone for sin and redeem lost humanity apart from the perfect, wrath-satisfying sacrifice that Jesus prepared Himself for in Gethsemane. The cup is a powerful picture of the wrath and judgment of God. Jesus became, as it were, an enemy of God, who was judged and forced to drink the cup of the Father’s fury, so we would not have to drink from that cup.
The struggle at the cross was first won in prayer in Gethsemane.
