The answer is that what we consider "hardworking" (a proxy for productivity) isn't the same as "working for a long period of time." (E.G.: Monitoring a modern irrigation system is productive. Carrying a few gallons of water on your head for two miles from the nearest stream takes a long time.) In fact, the OECD's richest, most productive, most hardworking countries have some of the shortest working hours. The bottom five, according to the OECD, are Denmark, France, Norway, Germany, and the Netherlands. All are richer per capita than Greece. All are technically "lazier" if you go by hours worked.
The missing key is productivity. Germans -- armed with large and scaled-up firms, low corruption, state-of-the-art technologies, financing opportunities, and smart global supply chain management -- get a lot more product out of each hour worked. So does the U.S. With the wealth that our productivity buys, Americans and Germans can afford things like leisure, or savings, or (in the case of the U.S.) lots and lots of stuff. Matt Yglesias put it simply, broadly, and truly: "Countries aren't rich because their people work hard. When people are poor, that's when they work hard."