These are only my best guesses and what makes the most sense in my head as to why. It is by no means gospel, and just because I have managed to reconcile a reason in my head still does not mean that I support any of this nonsense. I simply need some kind of logic for this for my own sanity, of which there is already little enough left.
I'd like to begin with Raoul. Poor thing was rather buggered over on this thing and I know that it bothers a lot of people. The need to vilify Raoul is mildly absurd. In the original musical he was brave and sweet, if a bit over zelous at times and not quite the quickest to catch on. But it was clear that he really did care for Christine. The closest you might get to saying something bad about him is if you see an actor who plays up the smarm. But that doesn't make him bad, just mildly annoying.
However, in the new sequel he has somehow become addicted to gambling, developed a drinking problem, and it is strongly suggested that he can be physically abusive at times. He is also short tempered, rude, and arrogant.
How in the world did our hero fall so very far?
My first theory is that Raoul was always prone to alcoholism, but kept it in better check during the first show. If you will notice he always has champagne waiting for him in his box and rather than opting to find flowers or some other trinket for Christine, he swipes the bottle of alcohol from the managers to bring into her dressing room.
I will further postulate that his family may not have been happy about his choice of bride. Obviously in the novel his elder brother was against his marrying Christine, so it is not unreasonable to assume that he may have been cut off after the wedding. He would have retained his title, but been broke for probably the first time in his life.
Financial issues are always difficult to handle, and it is possible that this turned him further to the bottle. There would also have been some amount of shame that he could not support Christine himself and that she would have to earn for the both of them. This may have also led to some amount of resentment and a feeling of frustrated impotence. He would have been raised to believe that the man was meant to be the breadwinner and care for his family. But he could not because he had no practical skills with which to earn an income, therefore putting that burden on his new wife who had just come out of a very traumatizing experience. What a horrible horrible thing for him to have to live with on his conscience.
I will assume that this is where the gambling addiction came into play. Betting was reasonably fashionable, and I'm certain he had friends who had done well at it. This would be a very attractive route for him to take. For a small initial investment he could multiply his returns quickly and easily if he won. It would allow him to take financial control of the household again. Of course since we know that he wasn't terribly good at it, that would add a new level of stress. Not only was he not earning money, he was losing it, forcing Christine to work harder to support them and their child, making him feel more guilty, making him drink more, and so on and so on.
Next we have Meg. How on earth did she go from being Christine's best friend, a sweet aspiring ballet dancer, and afraid of the Phantom to being the Ooh La La Girl and mindlessly devoted to him?
Let's remember that she was uprooted from her life and planted in a strange place where she wouldn't have spoken the language. The only people she knew and could understand at first would have been her mother and the Phantom.
Once she had realized that the Phantom was flesh and blood there may have been some fascination with him, especially since he would have likely still been rather solitary and mysterious.
Then we have the fact that she was basically whored out. It's entirely possible she contracted an STD from one of her partners. Perhaps something like syphilis. This would have caused some significant personality changes, as one of the symptoms of that disease is bouts of madness. I think you can see where I'm going with this.
As to her Carlotta-ish behaviour, I would chalk that up to the relocation and whoring as well. She had been a featured ballerina at one of the greatest opera houses in the world, and then suddenly she was just a nobody. She ended up doing cheap Vaudeville routines and sleeping around to pay the bills of the man she had become infatuated with. And then here comes Christine, who has become a world famous diva. She hasn't had to sell her body, hasn't had to live in a city she hated, she looks beautiful and happy. Then she is told that her old friend, who already appears to have the life Meg would have been able to enjoy if she had remained a ballerina and married a respectable husband, is there to sing and upstage her. It's no wonder she snapped.
Then we have Christine herself. The very best reasoning I have for her actions is Stockholm Syndrome and a rather complicated Electra complex.
There would also have been that fact that over the years, regardless of what she did her husband seemed to be growing more and more distant. Crawling into a bottle and lashing out at her for his own failings. The girl seriously has enough mental heath issues without Raoul's neurosis piled on top of it. She was screwed from the get-go.
Finally we come to the Phantom himself. Erik. How in the world did this psychopathic, homicidal, egotistical lunatic calm down so much so that he didn't even snap Meg's neck when she shot the object of his obsessive devotion? If this show were set about ninety years later I would say Prozac and fistfulls of anti-psychotics, as well as countless hours with a really good therapist. But turn-of-the-century psychology was somewhat lacking and not a pleasant thing to experience most of the time. So, how?
The only answer I can come up with lies in the ridiculous idea that after being intimate with Christine he left because he felt he didn't deserve her. I still can't quite believe that after so long he would have simply walked away, but we'll ignore that for the moment.
If he truly felt that he didn't deserve her because of who he was and what he had done, that may have forced him to take a very long, very painful self inventory to take into consideration exactly why he didn't deserve to be happy with her. If he cared deeply enough for her he would have decided to try and change himself. No more killing, no more stealing, no more practically everything that made him the Phantom. This would also explain why after so long he would have asked Christine to come to him. He may have felt that he had finally become the man that she deserved, especially in comparison to how her husband was acting. I'm sure that the press would have noted the change in him and how miserable Christine must have been.
So there are still momentary glimmers of how he used to be, but he had honestly and truly managed to change himself to what he hoped was a better person so that he could attempt to win Christine back. This would also explain why he was so accommodating to Gustave even before he thought he was his son. Showing Christine that he could be good with her child certainly wouldn't hurt his case.
