Quote by Michael C
In order to understand why this is so, you need to think about relativity of simultaneity. Imagine that observer B is standing at the midpoint between two trees, one "below" and one "above" him in your diagram. He sees the light hit both trees at the same time. Observer A, moving relative to B and the trees, does not see the light hitting the two trees at the same time.

In order to see the fallacy in the scenario you need to think about
relativity of simultaneity.