Translation: With the earlier concept of node translations in Drupal 6 you would have had a node for each translation. Thanks to the new concept, the translation is obviously done at the right place now and there is no need to sync content between several nodes just for the sake of translation.
Drupal Commerce: Another key factor was the E-commerce topic. Several people involved in e-commerce projects with Drupal 6 and earlier (in particular Ubercart and e-Commerce) started working together on a new project called Drupal Commerce (which is based on Drupal 7). That means a lot of e-commerce knowledge was brought into one single project. Drupal Commerce was in a very early stage (pre-alpha) when they decided to use it for the project but its architecture turned out to be very flexible.