Moscow 1980 was a bit of an aberration in that the US (amongst a few other countries) refused to attend so that naturally allowed the USSR the chance of winning many more medals than they otherwise would have.
Set in context though you've also got to consider a number of the results there dubious given there were noted and widescale doping programmes for a number of the communist countries. That's not to say that there couldn't have been clean athletes from those countries but unfortunately there has to be a certain amount of suspicion falling on the medalists in particular from that sort of time period.
I'd also point out that I don't think the other countries were necessarily clean, I'd suspect many weren't but perhaps weren't as focused on it as an ideological exemplar of the proof that their nation and method of governance was better. I think the Olympics and sport in general have made great strides in eliminating drugs cheats which might go some way to explaining some variance in the results.
The sort of drugs that made women look like men.