How come rocky found it so difficult to beat apollo, and yet russian 'ivan drago' demolished apollo with ease?

If Rocky had beat Apollo in the first movie there would have been no other movies. In the first movie Apollo won but know he had been a war. You think that's strange, in the fifth movie if I remember correctly Rocky beat a fighter from Kansas City which is not hard for that's how the script was written. The strange part is the fighter had to quit fighting because he test positive for HIV. Years later he is tested and he does not have HIV, who can he sue. This man was on his way to being champ. To me that is a better story.