Maybe some alien civilization does know about us, but it slightly afraid since we spec’ed in the war tree instead of space travel.
They kept letting us advance our war machines until one day they needed us. To help stop a greater evil; since they went space exploration instead of guns
This is my kind of thinking as well. While we may not be the only life in the universe, I imagine we’re not exactly a common occurrence. Uncommon enough that they have the slightest interest in keeping us from not existing lol. And when I say “us” I mean life in general on earth, not specifically humans. It would be a fair solution for an advanced species to remove humanity if it meant other life gets to live, and that’s unsettling/plausible.