How do I embed a vertical video?
You just need to right-click. Once you have the embedd code, paste it in the Video Embed box. After that, adjust the Frame Ratio of the video to a portrait ratio like 2:3. You need to play with the ratio or contact Youtube support to learn the exact ratio the shorts videos use.
Why do people make vertical videos?
An overwhelming majority of smartphone users naturally hold their mobile devices in portrait mode. It's easier and more comfortable. In fact, a 2017 study found that 72% of millennials never rotate their phones horizontally when watching videos, even if that means landscape videos appear tiny on their screens.