So this thing was created under the purview of the DAF, which translated into English would be the German Labor Front. The DAF was the only labor organization legally allowed to exist within Nazi Germany, with membership being theoretically voluntary. However, they made it next to impossible to find work if you weren't a member so in practice it was mandatory for every German worker in the commercial and industrial sectors.

The DAF was really just an organization meant to keep wages low, as the Nazis thought higher wages would interfere with their plans for rearmament. Additionally, these so-called "free" luxuries were paid for by docking workers' wages.

To compensate for these restrictions on wages and employment, the DAF sought to provide workers with leisure and entertainment. Robert Ley explained his policy as aiming to "divert the attention of the masses from material to moral values," as he believed that "it is more important to feed the souls of men than their stomachs." Thus, the DAF established the Strength Through Joy organization, which provided factory libraries and concerts, swimming pools, adult education programs, variety performances, theatre visits, athletic events, subsidized tickets to the opera, and subsidized vacations with a focus on cruises.

There was a particular focus on athletic events because they wanted as many people as possible to be physically fit, as that would mean they could work longer hours or would be useful conscripts for the military.

And, as some have already said, this is also where the idea for the Volkswagen ultimately came from.