Given the "nature" of 4chan (only a few hundred posts and a few thousand comments at a time, the vast majority of it shitposts and spam), it just can't do that. The imageboard format and limits basically prevent any scaling and mainstream success. If you follow any of the general threads in pol or sp for a while, you'll spot the same few people all the time, it's a tiny community of active users.

I think the logic is Pol didn't need to reach the masses, the masses only consume content they don't create it. You only need to radicalize the few people who then go on to be the 1% of people commenting and posting.