[kuschku]

Simply, because you don’t have to run them every 30 minutes.

In Germany and Japan on select few HSR lines trains are operating with a frequency of 2 minutes, and 800 passengers per train.

That’s 24'000 per hour.

[Animats]

The record is probably the Yamanote Line in Tokyo, with about 165,000 passengers per hour at peak. That's effectively a conveyor belt made out of trains; there's a loop in each direction with trains every 2 minutes in each direction during peak periods. Each train carries up to 1600 people, and there are 50 trains on the loops during peak periods.