I thought Bob Arum summed it up quite well...
"So I went to talk to Ali," Arum recalls. "He says, 'Jim wants to do what? Bring him here.' So I took him to Hyde Park in London, where Ali used to run. Ali said, 'Jimmy, here's what we're going to do: You hit me as hard as you can.' So Brown starts swinging and swinging, and he can't hit him. He's swinging wildly and not even coming close. This goes on for, like, 30 seconds. Then Ali hits him with this quick one-two to his face. Jimmy just stops and says, 'OK, I get the point."