It also helps that the whole thing is so otherworldly, the thinking mind is simply awed into silence. It takes a while before you could even begin to develop a conceptual interpretation of what is happening, and by then the whole thing is over and you are back to your sober self.
With other, long-acting psychedelics, there is plenty of time and opportunity for the mind to develop its own "spin" on the experience, and produce anxiety. Not so with DMT - it's like being shot out of a cannon and then coming back to earth just as fast.
It sounds terrifying and it is, when you're reflecting on it outside of the container of the trip. Somehow, while it's happening, you don't even have time to think about how terrifying it is, and as a result of that it ends up being OK. Tells you a lot about the nature of anxiety, really.