The big weakness of the Dark Forest scenario, is that if the galaxy was a dangerous place, it would already have been defensively/offensively explored. There w

The big weakness of the Dark Forest scenario, is that if the galaxy was a dangerous place, it would already have been defensively/offensively explored. There wouldn’t be a star system with primitives like us that wasn’t identified many millions of years ago. But for credible scenarios, your “too much smarter than us to predict” principle is a good one. “They went into another dimension” for instance, seems fantastical. But we have no idea what millions of years of science and technology will allow. For all we know, the re-acceleration of dark energy is the side effect of successive new civilizations harnessing the fine structure of space-time creating their own private megaverses.