Curl's success has more to do with it's quality (and ubiquity) as a C library. I think the curl cli somewhat got "taken along for a ride" with all the improvements that curl lib had by becoming the de-facto standard http library.
Because the library gets ported to every new platform anyways (it's what people use so will be the first to be ported to a new architecture or whatever) so the cli gets support for everything new "for free" so can outcompete wget (because it's always _there_ and works the same).
Now, there's also the fact that the curl cli is a fantastic piece of software, but in terms of features I don't think there's that much between curl and wget for simple cli usecases (but I still use curl).
Because the library gets ported to every new platform anyways (it's what people use so will be the first to be ported to a new architecture or whatever) so the cli gets support for everything new "for free" so can outcompete wget (because it's always _there_ and works the same).
Now, there's also the fact that the curl cli is a fantastic piece of software, but in terms of features I don't think there's that much between curl and wget for simple cli usecases (but I still use curl).