You are missing something.  In the morning when West Oahu commuters are leaving to go to work/school(actually besides students, many workers work at a school) in the Manoa/Makiki/Waikiki areas & they are all trying to catch the train at the same time, the Hoopili rail station will be a major bottleneck.  You can only load one train at a time and having a couple thousand people all trying to board simultaneously can easily cause an additional 1/2 hour or longer delay at the Hoopili station.   Also, unlike City buses on the road that can travel one behind the other, for safety the trains must be spaced apart probably at least mile which is the distance from one Oahu train stop to the next.  If there is a delay of one train at a stop, that will delay ALL trains behind the stopped train.  The train might have mechanical or electrical problems or if you have seen YouTube train suicides, if someone commits suicide on the Oahu train,  HPD will shut down the entire Oahu rail for many HOURS.