The major reason is that many amazon FBA failures are having limited product listings. Having a product that caters to small ideal customers can be detrimental in the platform. Here thousands of brands are thriving with their millions of quality listings updating daily catering to the large client base.
When your listing is too narrow, there is a chance that you become invisible in the eyes of the target audience. When they search for the product they want, they won’t get it in your listing and move to another seller.