> Why go out of your way to poison a no-name activist that operates in fringe circles for researching a story that nobody would care about, even if Putin were to confess live on TV channel 1?

I don't want to support or disagree with the following. I just mention that the possibility exists.

In such groups there are also lots of infighting. The more extreme a group becomes the more the extreme leaders also fight each other. So it's totally possible as well, that these guys killed and harmed each other. E.g. the guy killed the three guys and a friend of them poisoned him, or similar.