Drathnoxis:
Just *poof* all gone, overnight. I looked over the code of conduct again and I can't figure that they break any rules.
There's nothing specifically in the Code of Conduct that forbids threads like these, nor really should there be, but there is some logic behind culling the threads if they get too out of hand.
Solaire of Astora:
[T]hey were kinda stopping a lot of other threads with legitimate discussions from getting ... attention ...
This really covers the most of it. In short, the more a string of specific topic threads appear in short order, the more likely it is any other topic of discussion is going to get pushed out of public awareness and be denied the readership it could have thrived under.
The longer answer is more complex, but effectively boils down to the same thing. Not only does that sort of monolithic mentality do a lot of foster only a specific sort of discussion, but there are studies to suggest that it will also do a lot to foster only a specific audience. The longer people are exposed to like-minded individuals or topics, the more likely they are to either stop trying to post or outright leave the community entirely. It's that same logic that informs things like Megathreads, to prevent certain discussions or topics from single-handedly taking over the entirety of the forum population.
In short, fewer threads on a single topic will foster a wider, better, more participatory audience.