First of all. This game,, even though it might become great, is not the best thing since slized bread. It's a crpg. The third iteration in its series. People that haven't been interested in crpgs before have absoluly no reason becoming interested in this one. Not when the title has the number "3" in it. Some people might pick it up based on hype in media but not the majority. The majority of players bying this game will be people that has either fond memories of earlier Baldur's Gate games, likes D&D/fantasy crpgs or liked Larians previous releases and hopes this will have the same quality.
Without proper data you can't know for sure you are right. Honestly I'm not sure you are
I can ofc be wrong, I'm not all knowing. But from a logic point of view...why would someone that hasn't been interested in crpgs before, suddently pick this game up? With the game being titled 3 it tells the customer it's not the first iteration and therefor probably has a story that is continued from earlier games, a story they have missed. Being a crpg it will probably have some basic core mechanics that the customer haven't liked so far. Etc.
I personally don't like fps so I would never pick up a game tagged with fps, no matter how hyped it becomes. And I buy neither books, games or movie sequels without getting the the original first unless I can find confirmation that their stories are independent from each other.
Sozz answered it rather well on the comment below yours. I also think the fact that all the big gaming journalism sites already reviewed it even though it's early access (they didn't do the same for say, solasta) is also a small indication. I also can hardly believe that all the people who bought the game are hardcore bg fans. if that was true, why other crpgs don't get the same numbers?