You're putting a lot of responsibility on a license that has several permissive contemporaries. The original BSD license "Net/1" and GPL 1.0 were both published in 1989, while the MIT license has its roots set in "probably 1987" [1] with the release of X11.

No doubt, GPL had some influence. But I would hardly single it out as the force that ensured software stayed open. Software stayed open because "information wants to be free" [2], not because some authors wield copyright law like a weapon to be used against corporations.

[1]: https://opensource.com/article/19/4/history-mit-license

[2]: A popular phase based on a fundamental idea that predates software.