An irrelevant Dead Cells theory
Doctor Tom the 'Mushroomologist' was bribing Castaing the warden (who later became the Concierge).
Doctor Tom was a prisoner and mycologist who grew and sold hallucinogenic mushrooms in his cell. He made a tidy profit, and even had a cash register in his cell. When robbing it, the Beheaded comments that "Good ol' Doctor Tom here must have been supplying the whole prison." The man was audacious enough to have a sign outside his cell for all to see.
Castaing was taking bribes, but it's never confirmed who was giving them. While he is corrupt and incompetent, he's at least trying to keep the Malaise contained and the prisoners quarantined. So whatever the bribes were for, it wouldn't be for freeing prisoners.
What's the harm in letting these prisoners forget their misery, just for a bit? They're probably going to die anyways. So if Castaing gets a cut of the profits and looks the other way, Dr. Tom gets a cell with a secret garden and maybe some other small luxuries.
