It appears that the reason this page from a little-known website is able to rank amongst the bigger players is that the content itself is more focussed. It talks about how to name images for SEO, whereas most of the other pages are more general guides to image SEO—which all presumably mention the importance of naming images correctly, amongst other things.
Link roundups are selected and organized updates from bloggers that link out to their favorite content during a given period. Roundups are mutually beneficial relationships. It’s really hard to curate content as it involves a lot of work. The bloggers creating these roundups are actively seeking content to link to. You can land links in bunches. Over time, you will gain roundup coverage naturally. After you pitch the blogger who curates the roundup, you should connect on social media. That way, they’ll discover your future updates naturally. I’ve gained some backlinks from link roundups.
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.