In this case, from the pictures and comment, it seems to hardly need detailed investigation, clipping trees on the approach should be something that simply does not occur during VFR flying. So that leads to a pretty obvious answer - whether the engine was running or not I'm afraid.
How about pilot incapacitation (e.g. heart attack, stroke) plus a whole load of factors previously mentioned.
The logical conclusion of your argument seems to be that no properly flown aeroplane should crash, therefore all accidents are due to pilot error, isn't it?