Ubisoft says it was trying to put an ad for Assassin’s Creed Mirage in the main menu of other Assassin’s Creed games. However, a “technical error” caused the promotion to show up on in-game menus instead. Ubisoft says the issue has since been fixed
So they fully planned to roll out full screen pop up ads, it was just supposed to be in the main menu, not in-game. Fuckers.