The pendulum synchronization effect is the opposite of your claim. It has a physical causal reason for why pendulums become synchronized. Your claim is that it was random and independent.
Physically coupled pendulums will sync up (adjust their period to match).
But, physically uncoupled (fully independent) pendulums with differing periods will occasionally appear to take a swing or two in sync.
Polyrhythm is the relevant topic.
> all these services are individually down a lot, and the downtimes were bound to sync up
But the topic for that is the poisson distribution.