I'm not sure how much I trust those numbers floating around about the game's sales. The main source being quoted for the information is a Youtuber who hates the game and whose entire channel is about inflammatory culture war issues. In fact, if you search for Veilguard on Youtube, almost all the videos are about culture war issues, which might be turning people away from the game if they only read the headlines. You have to dig to find a review where they are offering an objective view of the game and not just ranting about the Taash character.
The game also came out days after the newest Call of Duty game, which is usually the biggest selling franchise every year. It may have sold better if it was released in the summer where there was less competition. Holidays sales will also likely help it.