I would guess that it is because of stale line up. There is Model 3, Model Y (which is Model 3 Wagon if that would be a European car) and now they come with a light facelift of Model Y. Model S and X are abandoned.
Compare it to European and Chinese brands, which are offering much wider range of cars and in case of European brands you don't need to travel to a different country to get your car fixed if it breaks.
Tesla worked as long as it had a technological advantage on its competitors (and when its competitors didn't exist at all). Now that the technology went mainstream and the competition is Chinese (high tech & high quality, much cheaper) there is no reason for consumers to choose an American brand. Also, Musk (at least the one that started Tesla and SpaceX, don't know now) isn't someone who's interested in competing in a mature market. I guess that's also the reason for pivoting to humanoid robots: gives him the type of extreme stimulus he needs to keep going.
Compare it to European and Chinese brands, which are offering much wider range of cars and in case of European brands you don't need to travel to a different country to get your car fixed if it breaks.