Interviewee seemed "odd". Stilted interaction during interview. Technical skills fine enough. Uncommonly, a second interview held with an extra interviewer brought in.
Technical director asked everyone; everyone said "no hire". Technical director hired him anyway, allegedly (but not proven) on the grounds of a bizarre, unshakeable faith in the supremacy of Russian programmers.
About day two, overheard on the phone apparently interviewing for another job. MD noticed he didn't seem to be doing much; asked if he had some work. "No." Do you want some? "No."
Gone on day three.
What went wrong? One person permitted to discount everyone else's opinion and hire a clearly bad candidate anyway, on the grounds of their own personal prejudices.