I just won my third war in C.O.C. and now I'm a level two clan. But, there is another clan that's won 21 wars and they're a level two clan also. I was wondering, how is it possible that our clans are the same level despite such a large difference in number of wars won?
The reason you saw clans with more wars won than you is because that wars that were won (or lost) prior to the update were not counted when adding the clan XP.
Only wars won after the update will count towards gaining Clan XP.