How strong is a chain link? How about half a chain link?
Chains do withstand all reasonable forces you can put at them. Current chains are bushingless design where the punched side plates have a half-bushing on each side. Not having a press fit bushing but integral bushing-halves, the bushing doesn't weaken the chain and the chain withstands a huge amount of force.
There are people weighing over 150 kg riding bikes standing on the pedals. The first thing that fails for them isn't the chain, it's poorly built wheels.
There are mountain bikers using chainrings as ridiculously small as 20 teeth. This gives more mechanical advantage for the crank chainring system, thus increasing chain loads. Chains don't regularly fail for them.
There are e-bikes that have pedaling assist at the cranks (mid-drive), thus increasing chain loads. Those e-bikes don't require e-bike-specific chains (except sometimes you see e-bike specific components; that's just marketers wanting to sell more expensive stuff -- normal bike components work just fine for e-bikes)
It's the straight upper run of the chain that bears the load. Once the chain turns around the sprocket, the load immediately reduces because the first tooth carries most of the load. The chain links flexing cause chains to wear, but the greatest forces are encountered in the straight upper run.
Thus, I'd say your chain had a manufacturing defect that caused at least one link to be weaker than it's supposed to be and thus caused the chain to fail. This isn't entirely uncommon.