Exactly, an average 12-14yo of modest strength could maneuver the chainsaw. The hard part about that work is doing it safely when unexpected things happen.
I have seen chainsaws that are huge, used in industrial logging. This section of comments is daft -- look at the size of the tree .. not "50 cm" trunk at all .. much larger. Secondly a boy of 16 can be anything between a helpless sheep to an olympian. Hard labor is not for all of them.
Yes, and the cut is very neat. Well, the cuts, actually, as we can see on the pictures that cuts were made on each side in order for the tree to fall in a certain way.
The person who did that knew what they were doing and knew how to handle a large chainsaw to fell large trees.