Humans use heuristics such as credentials to navigate an overwhelmingly complex world. They are not infallible but they are quick enough and right enough that we reach for them instinctively.
Explaining what a heuristic is does not address why one should be used in this case.
and it's often not the right thing to do. Let's say the blog post was from a top social media influencer. Would that carry more weight for you? We should look at the content of the post more than the poster.