While Pavarotti and his two sidekick tenors have been turning opera into a mass-appeal juggernaut, Bartoli has been trying to shrink a bloated genre.
Pavarotti and his sidekick tenors appeal to the masses. 
mnli hypothesis: Pavarotti and his sidekick tenors appeal to the masses.  premise: While Pavarotti and his two sidekick tenors have been turning opera into a mass-appeal juggernaut, Bartoli has been trying to shrink a bloated genre.