Go with the flow. Everyone's different and you get over each relationship at a different pace. I was with a guy for 3 years and our relationship became long distance and really did fizzle out, which sounds similar to your boyfriend's situation with his ex. I began seeing someone about 2 months after we split and can safely say that I was completely over my ex by this point, so it is possible that your new man is in the same situation.
Me and the second boyfriend ended up being together for 2 years. We split a month ago and I already know it's going to be months and months before I'm over this one. The moral is, every break up is different. If this guy didn't want to be with you he probably wouldn't be, and if he seems genuine, just go with the flow and let things develop naturally. Good luck x