In these opening sequences, Uderzo depicts a (nearly) victorious and thoughtful Caesar.
During the end pages, Caesar makes another appearence. This time he is angry. In about 46 pages, the visual depiction of Julius Caesar changes. He has a sharper, drooped nose and much more elongated face.
The readers are greeted with this caricature of Caesar in subsequent Asterix albums. Here is how he actually looked. (Or how the sculptor thought he should be depicted lest he be thrown to the lions!!!)
As a caricature, even the first one looked fine. But I believe the latter depiction has a menacing quality to it. Maybe that’s why Uderzo changed the illustration as the album progressed. I can only speculate.