Great Minds

It's been a month and I still can't bring myself to type out all that I have written in my notebook. What can I say other than yes, I am a lazy ass. Oh yeah, I can say - lucky you.
Anyway I have come across this saying many times and I have still not been able to fully understand it. The saying goes 'Great minds think alike'
In the book of idioms and proverbs that I have, it says it means that people having great minds think of similar things. To quote exactly ,'"Great minds think alike" means that great people think about things in similar ways' And I could not find the origin of this proverb anywhere but it has been used in French by Voltaire in 1760.

"“Comment les Grecs ont-ils mis en fables ce que les Hébreux ont mis en histoire? serait-ce par le don de l’invention? serait-ce par la facilité de l’imitation? serait-ce parce que les beaux esprits se rencontrent? Enfin, Dieu l’a permis; cela doit suffire.”

Voltaire,”Dictionnaire philosophique”, “Bacchus”"

So if this phrase is true, how come only Voltaire came up with it? There were many great minds during his time eg Benjamin Franklin ( I got a rant for him too ). Why didn't they think like him and come up with a similar phrase? Also if this statement holds true, then why do we need innovation. Or why are people who think differently given preference? You should think like other people. You are great. If you go search for diamonds that washed ashore, like a million others, you are great. because you thought like a million others. So is it that the more number of people think like you, greater is your mind?

So why should shakespeare be considered great? No one thought about writing tragedy, romance and comedy in plays. Not at his time at least. Why are movies which have a different storyline from others considered great ( of course this has to be accompanied by great acting and great music ) Oh and what about music. Why are Beethoevn, Mozart et al considered great? because they thought like others?

So next time someone says , hey this isn't different, this is just like others. You can say ' dude, I have a great mind. I think like other great minds '. Or something.

And one more thing. Is it great minds think alike simultaneously? or we don't consider the time factor?