There's a lot of factors that contribute to a high level of activity in the Political Subforums:
1. The deletion/censorship of Christian posts in broader social media. If you want to discuss politics from a Christian perspective, you have the choice of coming here, or getting your post deleted by Fakebook or another obscure forum for being too religious. Many forum owners will not allow political or religious discussion on their forums because it's "too hard to moderate" and I walk into their nightmare every day. Their cowardice is this forum's demand.
2. The article posting subforums (News and Current Events (Articles Required) and Current News and Events (Articles Required)) allow people to quickly generate a ton of new threads by copying and pasting article titles into the title box, the top of article text into the post box and copying the links to the article into the bottom of the post box under the article quote. Boom! 5 threads in less than 5 minutes.
By contrast, if you want to start a new thread in Theology, you have to actually think about what to post, and it could take you at least 30 minutes of thinking and typing to start your thread. Also, to respond to a theological thread properly, one is doing research, digging through their Greek concordance, their Scripture quotes, and their systematic theology, catechism (if applicable), creeds, knowledge of church history, getting all of the references - it's a LOT.
It's easier to respond to a political thread too - Google up another article, just post another opinion, emotional reaction, etc. You don't have to do all of that mental heavy lifting (or emotional heavy lifting, if you're posting in the Prayer Wall or Requests For Christian Advice). We live in a political ocean filled with shark politicians all looking for ways to kill us, make us struggle and suffer. It's easier to react to that than to do the hard work of debating a theological argument or caring for someone who is in need of help.
3. Unbelievers are allowed to post in the political subforums here, as well as believers in Christ. More posters allowed in a subforum means that you will get more posts there.
4. Emotion, fun, wit, and drama - A lot of the posts I see in the political subforums are jokes, and some of the jokes are funny. People are immediately invested in politics because they want to live another day without being inconvenienced or violently attacked. It's also entertaining in a dark way. The vast majority of people like action movies as opposed to reading books, and politics is like an action movie and a sports event rolled into one. It's entertaining, even though it has devastating real-life consequences for the losers of the game. Debating on an online forum is a source of entertainment for many, and the easier the debate, the better.
Despite all of these factors, I would not consider myself highly invested in the political sections. My heart is deeply rooted in taking care of other people in prayer or by giving advice, and casually debating the suffering of others is stressful for me. I would much rather debate an unbeliever in theology in the hopes that he would accept the Gospel or answer her question about Christianity. I'm not looking for entertainment as much as I'm looking to help others. Frankly, getting entertained by a debate has actually been a dark lure for me that takes me down a no-good road. But that is a story for another day.
But I do agree with you the social psychology that all too often seems to be present is, as you've qualified the dynamic, a "team cheering rallying cry" rather than as a moment by moment opportunity to meet people where they are as fellow humans beings and share our respective understandings about our faith in Jesus Christ.
I think this has to do with a lack of proper theological training within the Church. From the perspective of someone who has thirst for knowledge as a temperament, we've delegated too much theological training to the universities and locked it behind paywalls. I was fortunate to have Scripture memorization training as a kid and a mom who knew what a Strong's concordance was. Other don't have this gift. I honestly don't know how they survive.
But while my church has furnished me with a lot of classes on creeds, church history, Islam, finances, marriage, and so on that I've attended, debating theology here is still pretty much out of my league. Debating on this website period is out of my league - I don't have enough brain cells to keep up anymore. The intellectual vigor of discussion here is like on pastor level, seminary graduate level, something like that. The vast majority of Christians just can't keep up. It has nothing to do with apostasy. It has to do with time and temperament.
A Christian pilot for the missionary airlines that flies missionaries in and out of remote New Guinea is not going to be on the same theological knowledge level as the missionaries he's flying. He's providing a vital service for the Lord and is not an apostate. He has vital skills that are important, but if he walks into the Theology sub-forum here, the discussion may go over his head. Nothing is wrong with that. But the higher level you push the intellectual discourse, the fewer people are going to be able to participate. And that's not an insult to the Theology forums either. There is great value in being able to debate theology at a high level online, and the fact that this forum provides that is a service to the Internet. But to do that, less able posters are pushed out to get quality over quantity, and activity is a function of quantity, not quality, therefore you get less activity.
In short, it's all Clay Shirky's inverse power curve from
Here Comes Everybody. The higher the level of investment in something, the fewer number of people who will be invested. Difficulty has a parallel and inverse relationship to quantity of people who will do it. Politics is the easiest forum to participate in, low investment = biggest quantity = highest activity. Theology is hardest forum to participate in = highest investment = lowest quantity = lowest quantity.
On the third hand, the people in the Theology forums are the most invested, and thus more likely to pour extra time into this forum and stay for years and years because they are highly invested. This forum starts dying, they will be last off the boat. I know because I have seen other forums die. You need the whole curve. I saw one forum start off with a completely low-investment model and then switched to a completely high-investment model. Said forum died because they never had both at once.
This post is brought to you by my web design degree and 14 years of online forum experience watching forums live and die. This forum is still operating just as it should be.