Two reasons:
1. When googling things about politics/debates, I always found INTJf on the search results (in the form of a topic). I didn't know what MBTI was back then, I thought it was some political group, lol.
2. I then took the MBTI in college, scored ENTJ, got really curious, couldn't find a forum for them, and settled on INTJf as a next best alternative.
I mainly come on here to lurk in the politics/philosophy fora (not post, I don't think I'm well-versed in history), and can't help but comment on other sections.

I remember seeing the some some other forum, but there was just a vibe about it that put me off. IDK. Don't be too flattered though, you can thank Google and the lack of an ENTJ forum.
I'm actually only a mild E, and 50/50 on S/N and J/P, so I relate a lot to you guys, strangely.