Marvel was already aware than the Marvels will don't work (it's not really a surprise with the lack of promo):
https://www.hollywoodreporter.com/mo...ls-1235645119/
" But it wasn’t the first warning sign that something was amiss within Marvel in terms of quality control as Feige’s team went into overdrive producing shows for streaming; features Eternals and Ant-Man and the Wasp: Quantamania were also slapped with B CinemaScore, while audiences began complaining about keeping up with an increasing number of shows on Disney+ to understand the overarching MCU story."
"Behind the scenes, Marvel Studios and Disney were well aware The Marvels was in trouble before it hit the big screen. There was also a recognition that Feige and his team needed time to take a stock of their theatrical tentpoles, sources tell The Hollywood Reporter. On Nov. 8, Bob Iger said during on an earnings call that Disney’s movie empire has “lost focus” because of an emphasis on quantity over quality in the rush to feed Disney+ under the Bob Chapek regime (though it was Iger himself who initiated this push before Chapek’s reign.) Feige and his team felt this mandate keenly, to detriment of Marvel’s movies, sources say."
" Rather than being a straight-up sequel to the billion-dollar blockbuster Captain Marvel, The Marvels is something of a mashup. In the movie, Larson is joined by Iman Vellani, the breakout star of the Disney+ series Ms. Marvel, as well as WandaVision‘s Teyonah Parris as the grown-up version of Captain Marvel character Monica Rambeau. Mixing and matching characters for sequels is a game plan Marvel has used in the past on films like Captain America: Civil War, which featured nearly every Marvel character imaginable, but to much different results, grossing $1.15 billion in 2016.
“Why not simply make Captain Marvel 2? Why produce The Marvels when your audience identified, empathized, and even hero-identified with Brie Larson’s character? More importantly, why offer people similar or the same characters and stories that are on Disney+ if you expect them to go to a theater together? Disney/Marvel diluted their product,” says one film producer. “Of course, a picture works or fails for other reasons too, but losing so much value picture-over-picture is rare and hard to do.”
I feel they have sacrified somehow the Marvels with this mix between tv shows and movies, it's clearly the main reason of the bad box office imo (with the stike), but Disney plus is more important (in term of moneys etc...).