They have 3x the inventory also.
David vs Goliath.
If I may over-simplify to hammer home the idea... Each unit in inventory is a web page, agreed? That page has a little bit of SEO attraction potential (make/model/trim/miles/option/comments/location etc...) . The more units you have in stock the more "SEO potential" you have. Also, the more units you have on the ground the LONGER you can hold your shoppers attention PLUS, he more units you have on the ground.
One last inventory size connection. Generally speaking, the more units a dealer has on the gound, the more traditional media they deploy AND the more well known is the brand.
All this means is you'll have to try harder to get them and work harder to keep them there.