“”I wonder what Catholics think Christ suffered on the cross or why He did it.””
He did it to destroy death and for our Salvation that shows us love is stronger than death and sin
Let’s use the words of Blessed JP II since you want to single him out
From world youth day speech 2003
We Wish to see Jesus
http://www.vatican.va/holy_father/john_paul_ii/messages/youth/documents/hf_jp-ii_mes_20040301_xix-world-youth-day_en.html
Do not be surprised, then, when you meet the Cross on your way. Did not Jesus say to his disciples that the grain of wheat must fall into the earth and die in order to bear much fruit (cf. Jn 12:23-26)? He was indicating in this way that his life given unto death would bear fruit. You know this: after the resurrection of Christ, death shall no longer have the last word. Love is stronger than death. If Jesus accepted death on the cross, thus making it the source of life and the sign of love, he did so not out of weakness, or because he wished to suffer. He did so to gain our salvation and to allow us henceforth to take part in his divine life-Pope John Paul II
Why was suffering necessary to do that? Or was it?
How does that cross "save" us?