He's done cracked because Mueller wanted him to give sworn testimony to nail Stone, and he considers Stone his mentor and wont do that. So he's trying to give up all he can on others here in a desperation attempt to save Stone.
Nunberg introduced Trump to Bannon. Back in 2014 Nunberg has bragged how he listened to 1000's of ours of talk radio to "find" Trump's message he's then run on. Nunberg, Stone and Cohen were working for Trump's election along with Felix Sater for YEARS before Trump officially threw his name in. 2014 is a very interesting time frame because it's the same time the Russian Troll Farms were set up. It's mere months after Trump was in Russia for Miss Universe, at which time the pee-pee tape was supposedly made.