does having more posts than one time exact kw helps?

Does posting similar posts or exact keyword post more than 1 time with canonical to main page helps?
I have KW ranking for very long, and I see most of my competitors ranking above me having 8-12 posts of same exact keywords though only one post is ranking but why? and does it work?
I already posted 2 posts of the same KW and the results weren't great, the main post went from page 1 to 3. Any ideas?

Your site would need to be very authoritative to pull this off, which I presume it isn't.

In almost every other case, the posts themselves will get cannibalized, meaning, that only one of them will rank.

Try to avoid duplicate posts as much as possible
Instead, interlink them to pages that actually receive traffic