Not everyone receives the grace required to get to heaven. When the Catechism says that God predestines no one to hell, what it is saying is that God does not force anyone to go to hell because we all have free will. However, He is omniscient and exists oustide of time, so he already knows everyone’s eternal fate. This means that “before” God created us, (I put before in quotes because God does not experience time like we do) He knew exactly who will go to heaven and who will go to hell. St. Thomas Aquinas describes it well when he says “Predestination itself is not a property of those predestined but something in God: the plan in his mind destining some to eternal life.” The uncomfortable truth is that God knows some people will turn away from him but he does not give them the grace necessary to turn back. We all deserve hell, due to original sin and the further sins we commit, but God chooses to rescue some of us from that predicament but not others. I recently read about a satanic high wizard, Zachary King, who converted to Catholicism after a miraculous encounter with the Blessed Virgin Mary. It is wonderful that he was converted, but I also thought about all the other satanists who will never receive that kind of grace and will probably end up in hell. But that doesn’t mean there’s nothing we can do about it. Pray incessantly for the conversion of sinners. Pray the Rosary regularly, it is immensely powerful. Also pray the Divine Mercy Chaplet. If there’s anything that will save droves of sinners from the fires of hell, it’s God’s endless Divine Mercy. Hope this helped answer your question. Peace!