Longer content not only helps in adding more keywords to it, but there is also a natural emphasis on information. The authenticity of a post increases with longer text, which means that Google would recognize it as something more relevant than a shorter and concise text. As search patterns are synonymous with long tail keywords nowadays, a longer text also improves the chances of your article/website to be on a higher ranking than others.
One of my favorite ways to give content a boost is to run ads on Facebook targeting people with interests that are relevant to the content. It’s fairly low cost since you are offering a free piece of content. By targeting people with relevant interests to your content, you drive the right people to the content and into the top of your funnel. And if your content resonates with them, they’ll share, link, and engage with the content in ways that will help Google see its value.