Ah, RMS, if only we could all see the great dream world in which you live.
The GPL is a royally f'd up document. It could be argued that the GPL has spurred and invigorated the "free software" community as a whole. It was a unifier - a common ground which distinctly seperated commercial software and "free" software, something that the BSD license had failed to really provide.
But perhaps the GPL "won" not due to any sort of merit on its own part, but due to a collision of circumstances that enabled it to take the prize.
Linux (and by association GNU) started to enjoy meteoric success in the 90s, right as the iron grip of commercial software started to clench down around us. Proprietary, dreadfully expensive software was no new animal - but in the past it was backed up by proprietary, dreadfully expensive hardware.
The commodity PC and standalone commodity server introduced a whole new way of looking at things. Computing was no longer only for corporations - it was for people. And people need tools.
So tools were sold.
Ever since the PC itself became a commodity, people have started to question how something as intangible as software could in some cases cost many times more than the physical hardware on which it ran. Software always was, and in many areas still is, dreadfully overpriced in relation to the cost of producing it.
Free software - and hence the GPL - was a natural reaction to this.