The roads intended purpose was for public transport, business use vehicles, emergency vehicles and bicycles. They simply were never designed for the exponential increase in wear and tear. Like no-one involved in planning expected car ownership going from 1% of households to like 40% within a decade.

They would have built them sturdier to begin with if they expected heavy traffic regularly. It happened to China too, when we shifted from bicycles to personal cars, although it's getting better again with mass transit infrastructure being the focus of this century so far.