Take a look at this chart that shows the percent change in US sales (January - May) for luxury car brands. While Lincoln may have had a lower number of sales to start with, it is still quite the achievement to have this level of growth for Lincoln. If Lincoln can continue to keep up this level of growth as it releases more models in the future, then maybe they will really be able to rejoin the big leagues of luxury autos.
Another thing to look at is this chart that shows the percentage change in luxury vehicle price. As you can see, the trend is towards lower cost luxury, and Lincoln is near the forefront of this movement. What do you do if people can't afford luxury? Make luxury cheaper.