What's even more amazing is that there a lot more dudes powerlifting now compared to the 70's
the dudes in the 70's where using, but a lot less compared to now
I don't think this is right.
Firstly, the 70s raw records aren't comparable to what the best guys were doing from the late 80s to early 00s, because there was no raw lifting at the elite level during that era. The strongest guys of that era outside of the US, eg Fedorenko etc were doing amazing things equipped. We just don't know how strong they might have been raw in comparison to the 70s, because there was no comparison. Many of the strongest guys in the US and UK were doing multiply lifting, where comparisons were even more ridiculous.
Looking past the equipped era...
It is only in the past 3 years really that powerlifting has taken off, largely off the back of 2 big factors: 1) raw lifting - the equipment understandably put people off and made the sport less accessible for a long time; 2) CrossFit - of the back of which olympic weightlifting and powerlifting have both been beneficiaries. For the most part, powerlifting was no bigger in 2000 than it was in 1975.
It will take a few years for this Renaissance to take effect, but we are already seeing many of the old time raw records fall in the past few years. In Australia, there is so much talent coming through in every federation, it is ridiculous. If it was 10 years ago, most of these guys would have been doing insane lifting in the gym in relative obscurity.
Finally, more people were taking PEDs in the 70s than now. There was absolutely no social/moral issue with PED use in the 70s and right up until the mid 80s. Lots of people still use obviously, but there are a lot more drug free lifters. Guys like Mike T, Blaine, Ray Williams, are all going to surpass the 70s guys.
Oh...and human physiology has obviously not changed in 40 years.