Has you ever seen a Honda or Toyota plant ? Do theys have better metals ? Or just bolt things together more tightly ? What makes them so reliable ? And Do ya thinks it hads something to done with the nukes we dropped in wwtoo ? I asked this like Ali G to be funny. But seriously.
Both design and material quality, and a product of Japanese culture. Engineers that actually pay attention to issues that come up and invest in making them better rather than just accepting the warranty and recall costs as part of doing business. Giving factory employees the power to stop the line and deal with issues immediately. Giving accountants less power over the engineers. Embracing that which is honorable in giving customers a quality product, and supporting the dealerships in giving great customer support. Big American car corporations have such a massive customer base, they don't have to care about longevity or reliability beyond the warranty period. Japan is a much smaller market and reputation is huge.
