Things seem so much Greener on the other side?

To make a long story short. I'm not officially divorced yet, been going on 2 yrs and were close to the end. X husband had a girlfriend 2 months after we separated. Divorce papers hadn't even been filed yet. They have been together 1 1/2 yrs. I left a verbally, emotionally, controlling abusive marriage after 16 yrs. What I'm having a hard time with the most is understanding how he could be treating this gf and her kids so wonderfully. My daughter spends every other weekend with him and comes home and tells me all this stuff he's doing for her and her kids. Treating them way better than me and my own kids were ever treated. He even considers her kids to be there's together. Has pretty much blown off his own children which are 19 and 13. He still takes his daughter for visitation but always ends up at gf house doing her laundry, cooking, and running her kids. So our daughter gets drug along. He is also not working right now due to work comp claim and hasnt been since he met this girlfriend so he has to much time on his hands and has nothing else to occupy his time but kiss her . How can someone that was so evil be so different to the next one? I know this gf wont put up with his crap and he knows that. But I tried to stand up for myself when I was in it to and it made things 10x worst for all of us. But he also has no real friends (has run alot of them off) so he needs someone in his life. So don't think he is going to jeopardize loosing her if he would start to show his ways. She is controlling to and pretty much tells him what and when to do things. I just cant believe he is going along with it. He NEVER did that in our relationship. I could barely get him to help me carry in groceries from the car, let alone go to the store, put them away and cook her dinner, Do all her and her kids laundry. Keep in mind to that her kids are 14 and 11. Old enough to help out around the house to and dont'. He's even made comments before about them being lazy and doing nothing to help there Mom out. How long will this continue that he kisses her *** and lets gf and kids sit aside and do nothing??Don't understand. My daughter is just amazed when she is with him and this goes on. She lived 12 yrs of her life seeing him a totally different man. Why do guys do this and will it last???