It isn't random, in the sense it is always 2:1, but it is an observation not a logical inference or deduction; that is why I would not personally say it is logical, merely regular. Now, by observing that and similar things we can come up with models of election shells and bonding and all the rest and, using that model predict what the proportions of carbon and oxygen should be without ever observing it, then pat ourselves on the back when we do observe that we were right. But all of the logical manipulation is of the model, not the thing itself. You can say the proportions are logical but that is really just a shorthand for being what the model predicted.