I’m being pedantic but while external factors definitely can cause big jumps in tech, everything is always interconnected. We can’t discover rocketry without previous leaps in material science, those were impossible without manufacturing and mining infrastructure, those not possible without agriculture and sociological structures and organization, not to mention all the associated advances in mathematics etc
That's exactly the right level of pedantry. ;-) Right, I'd argue all of that is in the human ingenuity category.
But in contrast, if we knew that some invention like grinding lenses or whatever was completely impossible until some meteor or fungus hit planet Earth in year N and introduced a new element we were able to use, then that's an external factor.
I suppose there more pedantry is possible, like we could have invented space travel meteor-hopping tech by that point and discovered the "new element" for ourselves, but that's probably the wrong level of pedantry.
I think the closest practical answer is probably more along the lines of population density, and arguing that certain inventions would not be created until the density was enough to create a problem justifying its existence.
