The thing you need to realise is that different people find different takes on the same idea better than others. Maybe they find one author's writing style or presentation easier to follow than another's. Maybe they're a fan of said author, and enjoy hearing their takes on everything they write about. Or maybe they just one person's writing more engaging than another's.

Multiple people covering the same story isn't a bad thing, regardless of whether it's in the form of a blog post, video, podcast, TV show, book or any other format. It's like how multiple brands of sweets, soda or toothpaste exist.