Don't you think the league a team plays in could have an influence on them not having a backbone.
Having a backbone isn't something that just happens. It comes from building a culture out of getting yourself out of difficult situation.
It might be they're not out in that situation enough to have developed that culture.
No, it's about the individuals that they brought and the leaders that they established. Just think about Lyon who never acted that way in the 2000s, the gap was far bigger between Lyon and the bigger clubs but they always fought and always made it difficult for their opponents, with lesser players. PSG reminds me Garcia's Lille but on steroids, they play well and they can beat anyone but if someone fight back they fold.