It combined cheap GPIO for $35 instead of $500 with HDMI, tiny size, full Python instead of MicroPython, passive cooling and Linux.

Suddenly the Kodi and the GPIO crowd (Arduino, ESP8266, ESP32, etc.) could work with the same board.

A new era, like the IBM PC or the iPhone. Changed computing forever.

EDIT: like other commenters noted, it seems like it made the intel NUC a reality.