The crucifixion and resurrection of Jesus has a lot of significance in Christianity (possibly even in world history). But while Jesus died and rose again physically, there's another sense of Jesus dying and rising.
Paul describes that Jesus "died to sin once for all" (6:10). Many Christians talk about how Jesus is the one sufficient sacrifice that fits God's standards (as per Hebrew law). It also described how Jesus's death is a one-time thing (rather than a recurring thing) on behalf of us. Also, considering how Jesus was physically, mentally, and spiritually attacked on the cross (not to mention how one of sin's effects is death), in a sense, the sin of the world caused Jesus's death.
But Paul also describes that Jesus "lives to God" (6:10). Obviously, Jesus glorified God through the resurrection, but in a sense, all of Jesus's life (even before the cross) is dedicated to God. The resurrection feat demonstrates that God can overpower death.
Likewise, Paul calls us to "reckon [ourselves] to be dead indeed to sin, but alive to God in Christ" (6:11). Sin leads to death, but God provides live. Also, from the talks on baptism from the previous verses, the old self is considered crucified and thereby lost dominance compared to Christ's Spirit. So why rely on dead and busted lifestyles when we have a lifestyle based on God's provision of life?