Is not "none of them" but "all the ones that reached certain knowledge level", after you know something, you avoid expanding or showing yourself.
The dark forest idea comes from Liu Cixin Three Body Problem trilogy, if you show yourself you risk being destroyed by even more powerful civilizations that are hidden in the dark. And they are hidden because are afraid that the same happens to them, with a third one or with the one they destroyed after they advanced enough.
It is not the only possible reason, just one of the possible things that we don't know (or even don't know that we don't know) that can disprove or at least atenuate enough the paradox hypothesis.
Can be like explaining a caveman why you can't make a building high enough to reach the moon, so far he knows would be doable and even desirable for us, so why we didn't built one yet?
The dark forest idea comes from Liu Cixin Three Body Problem trilogy, if you show yourself you risk being destroyed by even more powerful civilizations that are hidden in the dark. And they are hidden because are afraid that the same happens to them, with a third one or with the one they destroyed after they advanced enough.
It is not the only possible reason, just one of the possible things that we don't know (or even don't know that we don't know) that can disprove or at least atenuate enough the paradox hypothesis.
Can be like explaining a caveman why you can't make a building high enough to reach the moon, so far he knows would be doable and even desirable for us, so why we didn't built one yet?