To be fair you need to take the 2008 swimming results with a pinch of salt. As per the article below (edited to make it shorter).
Overall, 25 world swimming records were shattered, the most in the sport since 1976, when
goggles were used for the first time. But there was a problem: According to Speedo,
98 percent of the records shattered were broken while wearing a specially designed swimsuit,
Speedo's LZR Racer.
Of the 25 world swimming records set overall at the Beijing Games,
23 were set while wearing the LZR Racer, a polyurethane swimsuit that covered nearly the whole body. This LZR Racer-wearing group included Phelps.
The effects were so powerful that they caused an existential crisis in the sport — the suit was that good. The coach of the Japanese national swimming team
broke an existing sponsor agreement to allow his athletes to wear the suit: "if swimmers don’t wear the LZR Racer, they won’t be able to compete," he said.
By 2010, the fate of the LZR racer was sealed: FINA, the international governing body of swimming
banned swimsuits that might aid speed, buoyancy and performance — including the LZR Racer. The wording of that by-law stands to this day and is clearly influenced by the science that made the LZR Racer so damn fast.