This ! Something smells foul in the state of Denmark... Nobody for years came close to the obviously drug fueled record and then slowly athletes have been chipping away at this non soft record. Similar to the old Eastern German 400 meter relay record that was unbeatable until fairly recently, PED regiments have been enhanced from the doped 80's in sprinting.
Drugs were never more potent than in the 80s, which is why so many of those women's records still stand (PEDs affect women more strongly than men). They were crude, brute force PEDs that are easily detectable today. The modern PED user is forced to use weaker drugs, and in shorter windows of safety from testing.
More subtle = less effective. Hard to argue with the brute strength and stamina enhancements allowed by 80s PEDs. The results speak for themselves.
So, why are we starting to catch up with a few of those records? A combination of today's weaker PEDs, plus faster tracks, better equipment, and a better understanding of sports science/training.
But even with today's PEDs and faster equipment and so forth, some of those records still seem far out of reach. On the other hand, if you put modern sprinters/equipment/etc. on 80s PED regimens, they would not only beat, but destroy the 80s records.