It does not occur to me that someone ever 'invented' a verb paradigm. Patterns are a natural feature of languages, and that is all a verb paradigm is.Does it occur to you, that, given someone, long ago, must have invented verb paradigms, they simply used a regular pattern of declensions?
Verb paradigms existed long before there was any writing.Why do you not assume, whoever wrote the paradigms just used a simple logic.
I suppose these just come from somewhere. I doubt anyone sits down and invents them; that would be absurd.It would be more difficult to think of different endings for all the various parts!
I don't know anything about Greek; I do know that there is no natural language too difficult for a normally-developing human brain to learn in infancy—making something even as complex as you've described linguistic child's play, pun intended.The full paradigm of an Old Greek verb is something like 181 words. One would rapidly run out of suitable endings, if one tried to find radically different endings for each part, not to mention the learning of such an animal!