Airlines frequent target infrequent members of their frequent flyer club in order to persuade them to fly with them again. It is not uncommon. MPC decided to offer something sweet for people who would have the opportunity to fly with CX again. But then again, it could also be a counter offer on a similar offer by AAdvantage though they only offered double miles for First, Business and certain economy class tickets only. In any case, the above offer was available to anyone with a US /Canadian MPC address. Yes, even DM members could register for the promo.

Although FlyerTalk is a place to gather round to talk about miles and such, your very first post to us seem to indicate that you're not as shy as most first timers are here.

In any case, welcome to FlyerTalk, and I hope you'll be able to contribute more positive posts in the future!