Why are these monster trains preferable at all? They apparently need distributed locomotives, which means that the number of cars per locomotive isn’t actually

Why are these monster trains preferable at all? They apparently need distributed locomotives, which means that the number of cars per locomotive isn’t actually substantially larger than a group of smaller trains. So they save a couple engineers per monster train at the cost of lower utilization (due to inefficiencies of loading and unloading)? What’s the corresponding benefit?