Luck certainly plays a role but a lot of people also keep creating content over and over that I feel has a much smaller chance of succeeding than other types of content. The million dollar question to me at any given moment is what are the video topics that have the most potential. Not all content has an equal chance of being successful on YouTube in my opinion.
I'm no expert by any means but I've seen enough to understand there is "some" element of control sort of like a good poker player. The cards may unfold against you but you can still analyze what your opponent might have and then determine what hands you want to play and what hands you want to fold and try something else. You can do everything right and fail, but you can also do everything right and have a lower chance of failing than someone who did everything wrong. I've created plenty of videos where I know the topic and presentation had a lot to do with the success and other topics with no demand would have failed.