He knew his best chance of beating Tommy was to brawl with the thin legged and comparatively weak chinned Hearns so fought accordingly. Hearns also broke his right hand, his best shot thus severely weakened.
Duran was his first MEGA fight and i feel he was a bit nervous or uncomfortable, Cholo also didnt fight with the aggression Hagler probably expected and trained for. Roberto Duran was also still a crafty talented fighter at that point
Hagler himself was slipping by the time he faced Sugar Ray, who moved and flurried making Marvin stalk him rather than staying stationary and trading with him. I thought Marvin won this fight though