Blue will grow fine in the absence of oxygen. It will not *bloom* in the absence of oxygen, though. In order to have internal veining, you must have cracks with air in them. Sometimes you'll see that the blue only grows where the cheese has been pierced. Sometimes, because the cheese has softened after you pierce it, the holes that you pierced close and you don't even get blue there. However, you'll get great blue flavour, because once the blue gets into the paste, it can grow right the way through the cheese.
To make a blue with great veining, you want a cheese that has an open structure. Remember that the curds will knit more easily if the pH is high. So one of the tricks is to get the cheese into the mold late (lower pH), don't press it, and then let it acidify to the point where it will hold its structure pretty well as it ages. This keeps the structure of the cheese open as it ages. However, it's a double edged sword. The lower the pH before you salt it, the less calcium in the curd and the *higher* the pH will go as it ages. This will soften the paste and it may well close all of those holes. So there is quite a lot of strategy involved in making a great blue.
Interestingly for me, Jim Wallace's Stilton recipe (which is apparently based on a pre-war farmhouse Stilton recipe) goes into the mold at a very high pH, which is pretty tricky to work with. When I made that cheese, I stupidly pressed the cheese "a little bit" and lost most of the veining (only the very center of the cheese survived). Great cheese, though. I'm definitely making it again when the weather cools down. I seem to remember that Aris's recent impressive blue was left to acidify for quite a long time before salting. That's probably one of the keys to their success.