How to use web 2.0 sites to rank?

Hi all, I'm new to SEO and I have a question about seo with regards to web 2.0 sites. Let's say you find a lucrative keyword that gets huge volume and has very little competition. For instance, I found a site that has a DA of 2 and no backlinks. This site ranks #1 for a keyword that gets over 1 million searches a month. This single page that ranks for the keyword gets over 800,000 visits a month.

​

Instead of creating a huge authority site to help me rank, why not post a well-written article about the keyword on a site like Tumblr or Blogger? Tumblr has a DA of 78. Blogger has a DA of 92.

​

Would posting an article that has onpage and offpage seo on a web 2.0 site get my article ranked
faster for this keyword? Instead of creating a 100 page authority site on my own domain, I can just piggyback off of Tumblr's authority.

​

What do you think?

Thanks