I don't know how people can say that JS is a great language with a straight face. Sure it has a lot of advantages mostly due to how widespread it is. But it's really obviously not a great programming language by itself...
Reality: JS is a great language, and that's why it won. The idea that it's merely the case that it was everywhere and that that is the reason it won is something that people who are sore tell themselves to avoid grappling with the truth. JS's ubiquity (a) was neither a fait accompli, and (b) is insufficient to completely explain its success—it only explains it if you're willing to overlook a lot of confounding factors.