How do we know that Jesus' death was a substitutionary sacrifice?

The concept of substitutionary atonement is central to the understanding of Christ's sacrifice. In 2 Corinthians 5:21, we read that God made Jesus, who knew no sin, to be sin for us, that we might become the righteousness of God in him. This illustrates that Jesus did not merely die as a martyr but took on the guilt of sin and bore the full wrath of God in place of sinners. Consequently, his death was effective in securing redemption for his people, making their salvation irrevocably linked to his sacrifice. If his death were not substitutionary, it would render the entire narrative of redemption meaningless, as it would imply that individuals still bear the weight of their sins.