Linux is not an OS. It's a kernel. The OS was GNU, and Linux was only the missing piece.
I maintain that any kernel that worked with GNU would have taken off.
However, what I got wrong: in the first years, Minix was not free. Users had to either buy the book, or pay a license fee of $69.
If Minix (or at least the Minix kernel), used the GPLv2 from the start, I wouldn't bet on Linux.
Also: I was thinking he's remained the leader of this very successful project, for a long time - he deserves credit for that. But perhaps that's a part of software's durable unfair advantage, that e.g. made so much money for Oracle, Microsoft. Similarly, BDFL, as for perl, python, ruby etc tend to stay there. So, perhaps it's more just not stuffing it up, than special credit?
What do ypu think of how esr explained linus's success in the cathedral and the bazaar?
Much of this can be explained because he was at the right place at the right time. Two very important reasons why Linux is so successful are GNU and the GPLv2. Any decent kernel could have taken off at that time. Linux was the first that actually worked.
Now the ability of Linus to retain leadership is remarkable. Just, let's not forget that he got a hell of a head start with the FSF's work. Both technical (GNU) and legal (GPL).