I would say it is true but more the entire environment. ~15 years ago in Sweden it was relatively easy to become middle class. It was for its time accessible and affordable to have things like education, housing and a family. At the same time it was relatively hard to become upper-middle class because of progressive income taxes, career paths and overall competition. That meant there were a relatively large number of people capable of starting and joining startups with low opportunity cost of doing so. Which also meant there were more startups who were interested in building something that is viable long-term rather than to cash out quickly.

(This isn't really true anymore but that is a different story)