As someone from East EU, this is actually plausibly accidental, though the timeline is suspicious.

Mushroom foraging is cultural, you can buy foraged mushrooms in farmers markets and in general it is a fairly popular leisure activity to go foraging in the woods.

I hardly know anyone over 50 who isn’t excited for the mushroom season, sometimes people do end up picking up a death cap as it can be mistaken for a couple different edible ones at its various stages of growth, though you have to be fairly inattentive to do so. That said we treat a couple of poisonings a year in our toxicoligy ward.

I don’t deny that the timing seems suspicious, would be awfully stealthy compared to the case of the killer windows and literally blowing up a plane. But I do suppose getting some powedered deathcap into his food would not be too difficult.

I do wonder if the motive would really be the recent moon failure, like would they really assasinate someone over something so petty? Maybe Putin was so desperate for a public win and he can’t afford to try again?