Nobody really knows for sure what the 2nd amendment is really about, but it's more probably about defending the nascent US against the Brits than acting as a quasi enforcement group. It's bear arms by the way, not sleeveless T shirts.
The thing is, that's right, it's sort of hard to know what it's all about (I'm certainly no expert, far from it), although if you take it in the context of the time it was written it makes it quite a bit simpler, like you said.
This is my take on it (probably some major parts wrong), first time I've actually looked at the timings of it:
So, it was ratified in 1791, what was going on then and before it?
Summary, how it seems to me (after looking at Wikipedia):
Up to 1500, natives and dinosaurs, Columbus popped in for a brew
1500-1760's - Various parts invaded/ colonised/ run by immigrants (us, Spanish, French etc), and seemingly we were largely taking the pi$$, naturally
1760-1776 - they had had enough of us and anyone else
1777 - Declaration of independence
1781-1787 - confederation of states and us consitution
1791 - 2nd Amendment
100 years later, civil war
So to me, that 2nd amendment was protecting against outside parties, rather than internal power struggles?
Now, the second amendment doesn't seem to be purely written based on 1791 either, it was effectively started in 1776 or maybe earlier, largely based on them gaining independence from others, not themselves. This was a time when the US was largely getting itself together, the issues they were seemingly more concerned with were external, and also founded on the below:
1) enabling the people to organize a militia system - not necessary in 2021, probably critical for US progression in 1780's etc
2) participating in law enforcement - not necessary in 2021, probably critical for US progression in 1780's etc
3) safeguarding against tyrannical governments - Didn't help against Trump, or any of the other morons
4) repelling invasion - Nobody is going to invade the USA, it could probably defend itself against the entire world, is part of NATO and has plenty of people on its side
5) suppressing insurrection, allegedly including slave revolts, though some scholars say these claims are factually incorrect - slaves are banned
6) facilitating a natural right of self-defense - fine, if it's from brit's taking the pi$$, not fine if it means walking down the street with guns, alongside 99% law-abiding citizens
But the above is seemingly what it is about, but what it's not about is full automatics and general day to day shooting up of schoolkids. Cops being fearful/ on edge from untrained and unhinged citizens carrying. Bringing in the military to police that and the police, who obviously can easily outgun any militia (as they have voted for like 4% defence spending forever).
It's not meant to be about the reds having guns to protect against the blues with no guns, or vice versa (as that was barely a thought back then), they vote the idiots in, they're hardly likely to take over and start shooting up the other half, albeit they've done stranger things.
It's weird, the gun totoers want the 2nd amendment, but they also want more defence spending, yet the 2nd amendment is meant to be about them being able to prevent the "tyrannical government", but they fund them more each year? All they're doing each year is voting for and enabling escalation on both sides. More guns, more aircraft, more bombs.
It could end in a civil war if they don't reign this in soon, but it won't be a fight of the free against the tyrannical, it will be lunatics with guns fighting decent people with limited weapons. The lunatics will become/ are the tyrannical.