By skyforbes First, the overall perception of CoD was already in the gutter due to how poorly Black Ops 6 was handled in its post launch, it already had generative AI assets popping up during its seasons and the egregious collab skins such as Beavis and Butthead and American Dad turned off a sizeable part of the fanbase.
Second, the marketing this year was ABYSMAL, the people more atuned to the marketing cycle of a CoD game have been served some of the worst delivered and contradicting information in series history, the reveal at the Xbox event immediatly turned people off from what appeared to be a neat new IP just to be revealed as a new CoD game.
CoD Next, their reveal event where popular content creators play the game and give feedback, was a mess, it generated barelly any positive buzz and what was revealed was generally unexciting.
The announcement that they would tone down SBMM and bring back persistent lobbies (two major complaints within the main core playerbase) was only made after the beta, when most people were already burned on the marketing cycle of the game.
Third, it's a back to back year in which, even if everything was perfect, players were gonna be burn out on the Black Ops subfranchise regardless.
Fourth, it's a more direct sequel to Black Ops 2, the least "weird" of the Black Ops games, so the choice of going for a fully hallucination induced mess of a campaign and tone directly contradicts the expectations of the fans of that game, especially the ones that hoped for a more grounded tone after the aesthetic mess that was Black Ops 6
This game has been a perfect storm of failure brewing for a while, it was very much agravated by it's bad campaign and shameless use of generative AI, but it was highly likely to underperform regardless.
It will (maybe) still sell "fine" by the end of it's life cycle, but it will take some serious heavy lifting to rebuild the franchise's image to a bare minimun of expected quality.