Because he was lying. Talk is cheap, and we avoid conflict by saying what we think others want to hear even when we know it’s not necessarily true. Or maybe he meant it at the time but changed his mind after he started thinking about why you guys split up in the first place. Or maybe he meant that he wanted you in his life as a person to ignore.
One question: are you sure he’s ignoring you? I assume you’ve given him plenty of time to reply, but if not, maybe he’s just busy. It’s the holiday season, after all. Or maybe he was abducted by aliens. They tend to be very active in the winter months.
If you’ve given him plenty of time to answer, then yes, he’s no longer interested in you, unfortunately. Or fortunately, since I’m a pessimist when it comes to rekindling broken romances. People don’t really change, and unless you guys have done some serious work on the issues you had while together — and by work I mean lifestyle changes, therapy, discussions — then the chances of succeeding a second time (or third, fourth, whatever) aren’t that great.
What you see as rejection might very well be a blessing.