I found the debate with Sikorski very illuminating. Sikorski is the foreign minister of Poland, with a long and distinguished career in the US (scholar) and EU (MEP) in addition to Poland. He's been in the dirt too, covered the Soviet invasion of Afghanistan as an on-location reporter in the 1980s. During the debate, Mearsheimer tried to lecture him about things that went on at diplomatic gatherings where Sikorski was present (and led a delegation) and Mearsheimer was not.
He's a total hack and his brand of "realism" has nothing to do with reality. Dude can't even read Russian, yet thinks he's an expert on Russia. The only reason we're discussing him here right now is because Russian troll army has been promoting him hard; like most charlatans, he has the appearance of someone who knows what they're talking about.
Mearsheimer says that there's no evidence Putin had imperial ambitions before 24 Feb 2022; that the war has forced him into this. Some of the closest people to Putin say that he told them fucking 20 years ago what he was going to do with Ukraine.