You see, Nikon was the dominant SLR maker before the digital age, and since 1959 millions of Nikkor lenses has been produced before the EOS mount format was even created. Canon had always played second fiddle to Nikon in the past. Moreover, Nikon had an almost 30 years headstart before Canon started selling their EOS based lenses. This is why, despite being the recent market leader, surpassing the total number Nikkor lenses ever to be manufactured is no small feat.
Having achieved that sealed the EOS system as the most popular SLR lens format of all time. Let's recap the road to dominance for Canon.