Because at these days, just a few compounds were available : test deca dbol and primo and there was no aromatase inhibitor, so the doses couldnt be high
Also a lot of different things :
- Today doctors follows the athletes
- Medications like statins and other stuff lowers bad cholesterols, lower blood pressure so they can blast with higher doses
- they didnt know how to properly run a cycle, they did things like pyramids (200mg per week then 300 then 400 then 300 then 200 etc), today pro have access to gear protocols that kick ass
- ALL THE OTHER STUFF : high HGH doses every day, INSULIN (!), IGF-1, etc etc
- New compounds (AAS)