No, successful bloggers are not encyclopedias. They are smart. They offer guest posting on their blog site. This means that they open their blog up to many people who want to start off blogging and get noticed. A person will write the article for the blog and submit it to the blog owner for approval. If the blog owner likes the blog they will post it on their site. At the end of the blog. the write has an author's box that tells people who wrote the article, what the website or blog site is and a short bio about the author. These blog sites have it set up for comments and they allow the person who wrote the content to respond to the comments left. They actually tell the person that they should respond back to all their comments.
The second way, a great site gets their blog posts is by paying people to write for them. The owner of the site will have a Write for US section on the blog. In this section, it will tell a person how much the owner of the blog is willing to pay, how long the article should be, and what they expect from a person.
You will contact the site with a short summary of what you want to write. If the owner thinks this is good they will ask you to write up the article. You'll submit the complete article to the site owner. They can accept it how it is written or ask you for changes. Once the article is posted on the site you are paid for your work.
Otherwise, it is up to you to do your own research and write your own articles. I own a review site that reviews all types of work at home programs that you can join to make money working online. I do all my own research, testing, and speaking with people who work on the site. I write up my own reviews. My plans for the future is to open my site up to other freelancers and offer them money for writing the reviews that are posted on the site. But until the website is making more money this is not possible. So for now, it is up to me to do all the work and research into the articles that are posted on my site.