From what I understand, its mostly due to the landing approaches being more straight forward, the lack of stacking of planes to land (less circling) and timing

From what I understand, its mostly due to the landing approaches being more straight forward, the lack of stacking of planes to land (less circling) and timing between planes is usually slightly longer than in the US. An extra ten or twenty seconds between planes taking off and landing can have a large impact over the course of a day. In the US the majority of flight delays are in the late-afternoon and into the evening because of the knock-on effect of delays (at that airport or others) and the lack of spare capacity within the timings to adjust the scheduling of takeoffs and landings.