In NL this often happens because of waterways. All starts off with good intentions, multiple providers, totally different fibers exiting the building in different directions. And then they have to cross a canal or a river. It's a 50/50 at that point whether they converge on the same conduit across the water.

I find intonation it’s better to select two competing provides as they are less likely to use the same ducts.

Had a few issues in some lamdlpcked counties on occasion - Kabul had all traffic routing via the same route into Pakistan for a few years, Kathmandu had an earthquake knock out both ISPs within 30 seconds of each other.

Backups via starlink global roaming work well now in particularly challenging environments.