Some of the problem is that groups overlapped others and were superceeded by new groups as they came out. For example:

Campagnolo Nuovo Record was the top dog through the late 60's up through the mid 70's.
Super Record was introduced in the mid 70's and at least some consider this a 'better' group.
Nuovo Record production was ended in the mid-80's about the time that C-Record that came out and thus became the new 'top dog' in Campy's line up. Super Record continued to be produced several years after the introduction of C-Record (aka Corsa Record).

And that's just the Record line. Mix in the multiple generations of Gran Sport (which was THE Campagnolo group before Record), Nuovo Gran Sport, etc etc etc. And as cyclotoine says you could take a year's course on Campagnolo history and still not have all the small details looked at in any detail.