If you compare the sales of Awakening compared to previous entries, you can see that word of mouth played a big part in why it was successful. Generally speaking, Fire Emblem games prior to Awakening sold to the core fanbase, but people outside just didn't get on board. Awakening stayed in top 20 sales charts for a few months, whereas previous games would typically only stick around for about 3 weeks.
Saying that "Marketing" is responsible for Awakening being successful and the other games bombing only demonstrates a complete lack of understanding, and intellectual laziness.