I’ll take a stab at it. (Protestants becoming Catholics)
Maybe they have failed to refrain from sin and hope that a more structured faith, or “religion” would be a better fit.
They can sin all they want and get absolved by an unseen priest instead of an all knowing God.
The Holy Spirit just wasn’t in them, so a “religion” less concerned about salvation and more concerned about rules, pomp, and circumstance, was more attractive to them.
You do not know much about Confession, do you? To be absolved the penitent must have true sorrow for his sin and a firm resolution to sin no more.
Reject the Catholic faith if you must but first take the time to know what you are rejecting rather than a made up caricature used to justify your own beliefs.
When I first understood the gospel (by reading John 10:27-30, actually) and the Holy Spirit opened my spiritual eyes and heart to receive God's grace, I knew immediately that this was the truth and I had had not been told it before. The idea that I would go ever back to Catholicism is foreign to me. I can't imagine any reason why I would ever want to. I know I have eternal life in Christ and I need never fear being cast out, lost or plucked from His hands.