It's making a joke that it was soon after Pizza Hut entered the U.S.S.R., and soon after they ran an ad with Gorbachev in it (https://www.youtube.com/watch?v=fgm14D1jHUw), the USSR collapsed.
THE COLLAPSE OF THE SOVIET UNION WAS CAUSED BY... A variety of complex socioeconomic circumstances, people longing freedom, the infeasibility of communist economic and social principles, etc.