Good Observation. Most people overlook the fact of the capacity of the restaurant and only emphasis than the crowd flow..

I noticed that most "Success" stories always revolve around food that are either easy to prepare at site or ready-made for delivery. E.g. Duck / Chicken Rice is always a popular success story. Noodles too as the soup based  can be pre-made.

So they are no longer bound to restaurant capacity, not bound to time (to make the meal) and excellent food QC because they can have all the time to prepare at home or before peak hour (Its their choice to control their QC and not rushed by consumers)