I can't say why you like it. People are different and all that. I can describe a few of its compositional strengths.
The gentle inverted-U curve of the upper edge of the main hill echoes the similar shape made by the top of the tree, considered as an outline.
It's bottom-heavy. Of course, you automatically get that with most daylight landscapes that include sky.
Within the tree (leaving out the trunk), the zigzaggy structure of the thickest and second-thickest branches keeps a viewer's gaze moving around without exiting. Furthermore, these lines are diagonals. I tend to prefer compositions based on diagonals over those where the strongest linear elements are vertical and horizontal; this may not be everyone's thing, I don't know.
Some areas have a lot of detail and others are plain. This difference is a way of introducing contrast (not contrast in the photographic sense).