Aestivation Hypothesis is just stupid.
Out of the 50 trillion galaxies, each with 300,000,000 stars, each star having at least one planet, there are millions, billions of civilizations ... all hiding. Animals in the wild hide from predators; they don’t just rest as that leaves them open for discovery. Predators eat weak animals when the opportunity presents itself and the target animal can’t hide or run away.
Life is about survival, survival requires resources, the more resources the more successful, the more competition for those finite resources, exposure means death and one less competitor.
So hiding is the best survival strategy; any exposure must be casually attacked, never frontally as that exposes the attacker to others. Use of scout asteroids like “Oumuamua” that travel from one system to another using the system star to slingshot on to the next possible competitors home system.
Casual attacks can take many forms like a slow moving projectile fired from lightyears distant that on impact cause a sun to nova killing the competitor without exposing the attacker. Or some form of slow moving ‘seed’ that on reaching its destination collapses the target system into a 2 dimensional object.
This hypothesis has many problems itself.
It sounds clever, but how do they know they need to hide?
What is the purpose of killing off other civilizations, when there is no gain from it?
I could may be see conquest. But you are hypothesizing just silly extermination.
Not necessarily hiding. Just not doing anything we can detect. Or more importantly not having done anything we could detect long enough ago for that sign to have gotten here. Detecting life across the cosmos isn’t easy. You have to have done something that detectable. Generally speaking we consider radio to be the first thing we did that could be detectable, and therefore on the list of things we look for. But even then that stuff travels at the speed of light, or slightly below it. If our very first radio signals were strong enough to survive in space (which they weren’t) they would have traveled through less than 1% of our own galaxy, and would be millions of years away from hitting another. Even things like rockets and satellites, you need a very strong telescope to be able to see them, and that “vision” still needs to travel at the speed of light. When we’re looking at planets hundreds or even thousands of light years away what we’re seeing is that planet THEN. If they didn’t have detectable life THEN we won’t see it. If it turns out 100 years ago some planet invented lighting their dark side, but they’re more than 100 light years away, we can’t see it yet.