So without actually seeing your code I can’t comment as to why the sphere wouldn’t be created in the viewport.
But I do want to say, that classmethods exist in python, and are often preferred over staticmethods. The reasoning is that if at some point in the future you need a reference to the class object, you have it, and if you don’t need that reference you can easily ignore it.
In general you can just use a function instead of a staticmethod, python is really flexible like that, not everything needs to be attached to an object.