Interesting you mentioned GPL proven to work in the Linux story. It was specifically GPLv2. I feel the GPL lost a lot of momentum with FSF's GPLv3 push. Linu

Interesting you mentioned GPL proven to work in the Linux story. It was specifically GPLv2. I feel the GPL lost a lot of momentum with FSF's GPLv3 push. Linus was publicly against it. Not only for Linux, but generally and philosophically against it. I presume a lot of others felt the same too. In theory you could continue using GPLv2 for new projects, but given that FSF had basically deprecated v2 in favor of v3, it seems that the momentum for v2 just slowly died out, and v3 was too controversial to gain widespread acceptance. Without a GPL default, the developers who didn't want to get too deeply involved in ideological questions probably just adopted MIT as the new default.