Michael really believed that all he had to do was be aggressive and Lennox would fold. And yes, Michael is a big man, but he doesn't use his height well. Plus Don Turner never gave Michael a realistic back-up plan, which meant that, by the time the fight came and Michael started having doubts, it was too late to change. There were those who came to Turner's defense. My feeling is that stage fright set in.
Some guys think they're ready to take center stage before they really are.
Whatever his skill level, Michael wasn't ready emotionally for Lennox. By the time he went down the aisle and up into the ring, he had an expression on his face like he wasn't there. And then, he didn't fight. Once the bell rang, he should have moved, jabbed, given himself time to get his legs under him. But instead, he attacked, except it wasn't really an attack.