Well, when something only last about a year I would hardly call that a "career", and it being derailed seems a legitimate observation. I have a feeling what you think they were paid is overblown, especially as much as some of them will blow through their money. It can go quick. In any case, being offered more than average porn performers isn't much to write home about either, and most of them that were to top UK talent probably did make out worse in the long run than if they would have played their cards right and had more longevity.
Plus, having the stigma of being in full hardcore porn is bad enough. Having to do almost all of your scenes with a dislikable slimball is even that much worse, so there is even more to it than the money angle.
