When more than one page targets one specific keyword, you end up competing with yourself. You are absorbing, or cannibalizing, your own traffic with these pages. As a result, each of them has less impact, views and even conversions than if you had just one landing page. I used to have this problem too. At that time I was working on a project - trendy kids clothes. Here you can learn more. It is necessary to check that the created pages do not compete with existing ones. New content should primarily fill gaps, not compete with itself for keywords.