I have to comment on this. The eagle may have become semi-domesticated or at least tamed to a certain extent because the owner of the cat has been feeding it. I am speculating of course. These two species may in fact know and accept each other. There are many unusual interspecies relationships which one would think were impossible.
But my initial impression was that because this cat or indeed any domestic cat rarely if ever meets up with a bald eagle in such close proximity, he or she was unaware of the potential danger and therefore stood up to the eagle. It was an unknown danger. However, we don’t know the backstory. My preferred assessment is the former.
Please remember that sometimes embedded videos on this website disappear because they are removed at source. This video comes from the Reddit.com website. No doubt it can be seen on other websites such as YouTube. If it has disappeared, I apologise.