Careful in overstating “Satan has lost”.
There continue to be souls lost to Satan every day.
We work with the Power and Mercy of Christ to minimize that number.
Jesus Christ with His death on the cross did in fact defeat Satan. To say otherwise is to give the devil power he doesn’t have. Without Christ’s suffering man would be eternally separated from God. Humans with free will can choose death of course, but to claim anything other than victory on the cross gives Satan more relevance than he is due.