Based on our current models, it takes a long amount of time for elements as heavy as oxygen to be formed, especially in large enough quantities that it can be d

Based on our current models, it takes a long amount of time for elements as heavy as oxygen to be formed, especially in large enough quantities that it can be detected. And when looking at a very distant galaxy, what we're seeing is an image of how it looked like very early in its lifetime. So, the expectation based on certain models was that oxygen would not have yet formed at the time in the history of the universe when this image left towards us. The expectation is indeed that all galaxies will have more or less the exact same elements that we have at ~13 billion years of age. But the image here is from a galaxy that was, at the time the image was emitted towards us, much younger than that.