According to studies of Siberian scientists, the crater formed during the 300-350 years since the end of the beginning of the 15th or 16th centuries. The zoning of the crater caused by geological processes and intensive introduction of deep gas flows of matter, which led to the transformation of silicate rocks within the crater. "An important confirmation of these ideas were the result of s geophysics from St. Petersburg (SB State University of Mining) and Yekaterinburg (Institute of Geophysics, UB RAS). Performing gravimetric and geoelectrical investigations in a professional manner, they also came to the firm conviction that Patom crater has a depth of an endogenetic nature ", – said Antipin. source
From this, I infer the gist of the matter is that it was an earth fart, rather than either a volcanic or cosmic event.
A gassing event would explain many, if not all, of the reported sicknesses, avoidances, and deaths.