Russian Doping
The reason Russia got banned in 2018 was because of their performance in the 2014 Games. The McLaren Report discovered that, leading up to the 2014 Sochi Olympics, many Russian sports federations had covered for athletes who had participated in doping. Over 1,000 athletes benefited. 43 Russian athletes who competed at Sochi were subsequently disqualified, and 13 were stripped of medals.