I couldn’t find how they got the “private” opinions out of people. Individual interviews vs a group setting? Otherwise don’t see people revealing private opini

I couldn’t find how they got the “private” opinions out of people. Individual interviews vs a group setting? Otherwise don’t see people revealing private opinions to some random person on the phone. It’s not unlike seeing high support numbers for Putin in Russia. “Hi! We are from a totally independent polling organization. Trust us. Tell us how much you hate our president.” - “Oh, right. He’s fantastic. Please, sent him my greetings and well wishes!” Obviously exaggerating here, but wondering how they managed and accounted for that effect.