Apollo Creed over-trained for the rematch and went into the fight already exhausted.
The first film could've been a true story. The only scrap of Hollywood bullshit in the entire film is Rocky's first punch knocking down Apollo. Everything else is true to life with the film even acknowledging that Rocky's only able to hang with the champ because Apollo didn't train for the fight.
The sequel has Apollo training like a man possessed. By his own admission, he's never trained harder for a fight. Conversely, our hero has just six weeks to train for an undefeated Muhammad Ali stand-in who is obsessed with beating him. The only way Rocky could logically make it past the second round is if Apollo entered the rematch half-defeated. And since Rocky getting a couple of body blows toward the end of the bout seems to even the score after 7 or 8 rounds of domination from Apollo, I'd like to think that I think Apollo suffered a rib injury while training.
I like to believe this, especially since Rocky admits to Adonis that Apollo beat him during their fight in Rocky III. ---
