I'm not Catholic, or religious at all, but I've had the same question. They don't "idolize" the saints. To them praying to a saint or depicting them is more of a conduit to God. They see it the same as asking your neighbor to pray for you/a loved one. They believe saints are messengers delivering their prayers to God.

Because Arabic and Jewish culture value the uniqueness and singularity of God, while the Pagan cultures of Greece and Rome (where Western Christianity developed) valued multiple persons in divinity with responsibilities over different aspects of life.

When Christians were oppressed by Rome, their crime was not worshiping Jesus. But rather their refusal to participate in ritual or pay respects to the other official State gods.