No, not that they were based on an existing Japanese toy line, that’s already known. But rather, who was it that came up with the whole back history for the American version, effectively creating the mythos as we know them today: JIM SHOOTER!!
Who? some of you may ask.
This guy: http://en.wikipedia.org/wiki/Jim_Shooter
OK, here’s the story: Shooter was the Editor in Chief at Marvel Comics during the late 70s/early 80s.He’s remembered today mostly for having been “among the MOST HATED EICs that Marvel ever had” (second only to Joe “I’ll have Spider-Man lose his marriage by having him make a Deal with the Devil” Quesada) because of his supposed tyrannical style of leadership. But he also happened to be a pretty good writer before that.When Hasbro came to Marvel to make a comic book based on their new toys, they let them come up with the story. That I knew. Here’s what I just learned: Shooter hated the stuff his writer came up for the Transformers’ series bible so much he REWROTE IT HIMSELF. So, everything from their classic origin- the war betwen Autobots and Decepticons, Optimus Prime being such a Good Guy Badass, etc.- came from him! Or that’s what he alleges in this interview: http://www.nycgraphicnovelists.com/2010/07/jim-shooters-secret-origin-in-his-own_26.html
Important quote: “I wrote Transformers back story and bible myself – for free, having already paid O’Neil the money in the budget. The characters are named after my relatives. I came up with the origin of the war between the Autobots and Decepticons, planet Cybertron and everything else. The only thing I kept of Denny’s was the name of the ship, ‘Auntie,’ at least in the first treatment.
(Note: when he says he named the characters “after his relatives” he presumably means the HUMAN characters in the story, unless he knows people named Optimus or Megatron. 
)
Of course, he might be making all that up. But I doubt it- I’ve followed Shooter’s career for a long time, and while he’s definitely a stubborn kind of person, he’s also been surprisingly open and logical-sounding. It is very likely that the stories of his being an abusive boss are exaggerations of the stuff he had to do to keep Marvel afloat (see the article for details.). So I tend to believe him, though with a grain of salt- we’re all biased after all.
The interview is worth reading by itself, as it gives a detailed behind-the-scenes look into the world of comics publishing. Who’d thought it was such a cutthroat business?
And remember, next time you say, “OPTIMUS RULES!” you know who to thank now.