Maybe reducing the world population could, if not cause technology to get stuck, at least slow down technological development compared to OTL. Possible PODs might be no Green Revolution, or some oilfields not being discovered, leading to a higher dependence on biofuels and consequently less space for growing food. A smaller population would mean (i) fewer people available for technological research, and (ii) smaller consumer bases, meaning less money from sales to reinvest in development.