He knows how to bullshit is about all and we all know that means habitual lie. He's practised it for decades and were caught outright bullshitting. So Obama thought he'd be the perfect rube to use to destroy the country.
I'm convinced it didn't "go wrong" but went right for Obama. Destroy America and blame the old senile white guy. He didn't pick Biden for his intelligence.
You're right he's an easy scapegoat, and you saw through the classified documents, he's an easy scapegoat that due to his dementia they choose not to prosecute. It's ideal for Obama's plan.