Well ... here are some ideas to toss around:
The Charioteer is a conqueror, leaving his conquest behind without a thought and moving on to his next one. But what develops in conquered cities if you don't leave enough infrastructure behind to keep the populace in line? You see, he isn't a victor or a master ... he's a conqueror. On all planes, perhaps, as Waite suggests, but because he's in spot VII, the end of the first septad, he's only the 'master' of the material world. Not of the psychological world (the 2nd septad) or the spiritual world (the 3rd).
This is neatly alluded to by the starry canopy. Were you to ask the Charioteer about the heavens (about spirituality) he could only point to a painted representation of it - an artistic rendering, not the real thing. He cannot get guidance from the stars because of his own self-conceived vision of what they look like (and, of course, because he's not looking at the stars, just a painted canopy representing them). It's the concept of heaven for those who cannot see it. He's not ready to see it, so a picture must suffice.
Another interesting point about the Chariot is that while the conqueror thinks he's off to his next conquest, he can't possibly be. His engines (the black & white sphinxes of duality) are lying down on the job. Without mastery of the other septads, the material world is all the conqueror can have.
The Charioteer thinks he's running the show, but he never looks back, he really can't look up and doesn't notice that he's not moving forward.
Sorry to run on so, off-topic and all, but the starry canopy has (IMO) to be seen in the context of the whole card.