At last week's Open 2020 Summit we had a video address from the Prime Minister of Australia, Kevin Rudd. I noticed that the MPEG file for this was much smaller than the videos of the conference presentations (13MB versus 130MB for a four and half minute video).
If you look at the PM's video you will notice that the background is very static, as his body. The result is that the video compressional algorithms need only animate his head. The conference videos have the presenters waking around in front of a flickering screen and so are much larger files.
This is something I also noticed years ago when looking at JPEG compression of images: photos taken by professional photographers seemed to compress better.