As someone who has personally used a chainsaw for many years I saw that video with interest but realized quickly it's faked. It takes a substantial amount of force on a chainsaw to keep it cutting. A real chain saw is a relatively heavy device. I see no evidence in that video that the chainsaw is in fact cutting anything while only under the forces afforded by the drone. Every cutting shot is from closeup and I did not see a single shot of it cutting from a distance. Either it's very poor choice of editing since it doesn't show what the whole video purports or it's a fake.