As mentioned in our Mac and Windows guides to compressing your videos, getting good at compressing takes practice/experience. The goal is always to get your video file size to be as small as possible while still delivering great picture and audio quality.
Andy Owen at Techsmith has an excellent article on how to improve your compressions.
Mike Osterman notes the following, which is related to the article above:
"When you put a little box with your face on the screen*, there's a potential side-benefit of smaller video file sizes. When having to do some compression of videos so they would fit in the "media comments" for the COVID-19 course, I observed that the videos with less full-screen video of people were much smaller, and often didn't need to be compressed. This makes sense, because less change in visual information from frame to frame means less information to encode. The section "How Much Action Is In Your Video" in Andy Owen's Techsmith article goes over this topic a bit."
* By "little box with your face," Mike is referring to what is known as "Picture in Picture" or PIP. You've likely seen this when you watch a video of someone's Powerpoint presentation, and in the lower right-hand corner, there's a small video of the person who is giving the presentation.