<WaywardHorizons> In the very early 2100's, there was a period of extremely fast mass colonization that had almost no governmental supervision.
<WaywardHorizons> And after it abruptly ended in 2110, they managed to get their pants on and started work on obtaining the colonies for themselves.
<WaywardHorizons> But due to a previous spreading out over the solar system, actual "nation capitals" had been moved into space stations or otherwise off-world.
<WaywardHorizons> With all the attention being focused away from the solar system, I'd imagine a new government could form (or one splinter off of an already-existing one), take over Earth and some nearby objects, and then while trying to set up their own defense mechanisms, ends up tripping an older system, which sends out missiles everywhere and causes it to collapse.
<WaywardHorizons> The resulting civil war lasted for slightly less than a decade and was confined almost entirely to Earth and Luna.
<WaywardHorizons> But it was intense and left the Earth inhospitable to life in a disturbingly high number of ways.