I always had the idea of Blacktron and Futuron happening after the classic space era, when minifigs settled in space permanently. The classic space era promised a new age of technology and living for an optimistic Lego galaxy.For humans, a task of this feat had never been done on an interstellar level. It would surely put the human race on the galactic map. Everything was checked and checked again. After getting to the first few systems, everything was fine. Research was done, star catalogs were expanded more than ever and the hope of discovering extraterrestrial life was around the corner.
It all seemed swell, until a dispute with commanding officers went so far that astronauts felt demotivated and wanted out. The era of happy optimism was on its knees. Few astronauts were truly happy, and decided to band off as Futuron, and pretty much fleed before everything went downhill. Fights broke out, until a war raged across multiple solar systems. Eventually what was left decided to also band together as Blacktron.
Futuron aimed for a better future, while Blacktron was more aggressive, lashing out at other systems, trying to grow and take over as much as they could, like wandering nomads. Blacktron, due to their aggressive nature stuck around far longer as Futuron eventually faded into other groups. This earned humans a bad rep, thus the reason there were alien invasions later in the future.
This stuff is kinda fun to think about actually.
Sorry for going off onto my own thing.