Light travels slightly less than 1 foot per 1 nano(billionth) second. Electrical impulse through wires is considerably slower due to magnetic induction and electrical capacitance effects slowing transmission of a signal.
One variant of a thyratron was sensitive to light, so a sudden shift to a sufficient light level would trigger operation and switch electrical flow through a high voltage transformer.
The output of the high voltage transformer was used to initiate a short circuit between the contacts of the trigatron, a type of switch, placed between the capacitor bank and the coil of the shutter device.
The discharge pulse of the capacitor into the wire transmission line would reach a camera’s shutter and trip an exposure. The longer the distance from a capacitor to a camera, the longer the time delay until an exposure occurred.
Arrange cameras at properly chosen time intervals dictated by propagation delay along a single transmission line, or multiple parallel transmission lines of different length all synchronized by the firing of a single thyratron, and sequential photos can be captured.
I really wondered if they had not used some kind of light sensitive switch. That would make the most sense.