They weren't created to protect the autobots, they were in the very far future of the Transformers (like 200 years or something like that) and had evolved to the size of a little larger than humans (or de-evolved as some might say :P). Hence the reason that when they found the Ark (As they ended up being on prehistoric earth, due to a 'pioliting malfunction') that is why all the autobots and decepticons were so huge. They were basically former versions of themselves.
And the reason for the same names, is they chose to take them, out of respect (and Megatron, simply because he was egotistical)...I think...that part I'm a bit hazy on. But I know they weren't the originals at all.