Lee was in bad shape and since Steward seems to have a close relationship with him. Living in Steward's house and Steward saying they were like best friends. It makes sense then since they are so close.
What was Lee thinking? Bad defense by Lee, also bad stamina as well. I think Lee was overconfident coming into the fight, Lee was expecting Vera to be koed, but no, he kept coming and ate Lee' shots.