Vox is an online-only news publication platform. They aim typically towards a younger audience, and as a result YouTube videos are a large part of their company. Of course there is the website with the articles and the Instagram account with posts about current issues, but the main thing are the videos. Vox's videos are their most popular part, I knew about Vox originally not through Instagram, but YouTube where the videos often are in the "Trending" section. This makes them even popular than the website and is thus a necessary part of the Vox media.