I never bought into the claims that Jared Diamond is some sort of racist; he book is plainly anti-racist and anybody who says otherwise probably never read it. Honestly. That said, some of Jared Diamond's arguments are really lame.. just poorly thought out. For instance, is claim that the use of wheels for transportation is in some way gated by the availability of pack animals. This guy has never used a wheel barrow…
Ox-drawn plows are at least 4000 years old, and I feel like seeing an animal pulling a plow all day begs for wheels so you can pull anything anywhere. At least more than the combination of a wheel and a stick, to apply mechanical advantage to lift and then move things.
The oldest wheelbarrow that we know of is from ~200 BCE, and the oldest chariots from ~2000 BCE. This tracks with animals pulling your stuff either being more obvious or to there being a higher ratio between payoff and cost of development.
You're right that it often comes down to dumb luck, but I think those lucky moments are usually facilitated by other factors. That's why there are often simultaneous and independent inventions (multiple discovery), and why tech startups aren't geographically uniformly distributed.