The field does look big but its always very difficult to tell from a photo. The first photo shows trees circa 200m away, the second shows something just off the left of the photo within say, 50 - 100m. The third, trees probably 3 - 400m, the fourth photo, possibly 2 - 300m, and the last, less than 100m?
It does look spacious certainly but if we assume that he landed on the edge of relatively large open space, then perhaps it is fair to say there may not have appeared to be a sufficiently lengthy clear run to get the aircraft down in.
It also seems clear that the ground is farmed and certainly appears to be relatively flat and firm. However, this is from the ground. From 2000ft up, you just don't know and thats the bottom line.