You’ve probably heard the overused term “pivot to video” at some point, which is both a joke about and an acceptance of the fact that many publishers are pushing their resources into video. Video advertisements are more expensive to buy than banner ads because they lead to higher click-through rates, which means a business can potentially make a lot more money through video than through other forms of content. So, if you can create great videos that make people want to watch and that drive ad revenue or subscriptions back to a website, you can become a very valuable asset.
The topic you choose must have enough depth that you can create a lot of content for it. This is important for building an authoritative site, for search engine optimization, and most importantly, for the end user. If you don't have enough content about a topic, you're not going to be taken very seriously as an authority on the topic and it's unlikely you can convince someone to make a purchase from you.