Mushrooming is common, poisonings are quite rare, because there is no reason to take mushrooms you don't know - there are enough ones that are clearly good and you can easily throw out anything which is even a little doubtful. Common poisonous ones look very distinct, and you can easily avoid the doubtful ones. And most of poisonous ones won't kill you (though you may wish you were dead for a while). Really bad ones will, but those are widely known and nobody sane would touch them.
I knew many people who regularly collected mushrooms, and did it myself, never heard any cases of fatal poisoning. It's not that it doesn't happen at all, but - especially among people who do it regularly - it's pretty rare and usually happens when people try something "exotic" or buy from untrusted third party.
In this particular case, of course, it's pretty clear shat happened - same thing tgat happened to all thise people falling out of the windows and the same thing that happened to Utkin and Prigozhin. Putin happened.