There was a time when many computer programmers cared less about making money, and more about principles. I don't mean that pejoratively.
It was a simple, arguably naive mindset, and we had somewhat utopian beliefs about the impact of Usenet, and later the Internet, on society. We programmers were often middle-class, students or staff at universities, or industrial scientists or engineers of some form or another. We were well-paid, with stable jobs, and the privilege of being able to share our software with others on terms that we would like to have their software shared with us.
The GPL was basically pushback against a piece of commercial software for which source code was withheld. Stallman never wanted to personally suffer that again, and his solution was to rewrite the world with a viral license that would ensure he needn't. And it was hugely controversial because of the constraints that imposed on people who wanted to use GPLed software.
Constraints on "fields of endeavor" were controversial too, but idealism won out in the Open Source Definition. It was a revolution, after all.
The decline in popularity of the GPL has been interesting to watch. People adopt the MIT/BSD-style licenses because they're easy to use, without really thinking through what they mean. For those who didn't experience the contest between Open Source and commercial software, choosing a license might even seem like an annoying triviality.
Until quite recently, the notion that a program might have 100+ million users was fanciful. Despite the utopian views of how computers and networking might evolve, very few (if any) FOSS people seriously considered what it might mean for billions of people to use computers, especially from an economic point of view.
The successive waves of commercialization from the Internet boom leading up to the "dot com crash", startup culture, cloud computing, and "social networking" (which has well-outgrown that name) have seen programmers' collective views change. In part, people shed their earlier idealism, but also demographics changed as more people became programmers, and the world changed too as well-paid stable jobs have largely disappeared.
Open Source (and Free Software) were products of their time. And in that time, no-one in the FOSS world conceived of their software being used as exploitation: we were displacing proprietary software! Some people maintain that idealism today. Others would like to see a different sort of fairness, and perhaps we'll see a new generation of licenses developed to address this new world.