Here's an example video: https://www.youtube.com/watch?v=Wyyzi6l7n1U
His spamming has had a negative impact on YouTube and it's search function.
So my question is then, why hasn't YouTube taken any action against him or his channel?
Demonetisation is the worst that YouTube will do to a channel - no money = no incentive to post.
But they very rarely ban a channel from posting.
Also, the people who review channels are just human. They can be arbitrary, random and unfair.
At the end of the day, if no one watches his videos then they won’t show up in the search results.
Maybe, but no rules are broken, so no reason to act.