It appears to me swimmers are more fit than runners as they tire less the further their event goes.
Looking at it roughly timewise:
50 free = 200m
100 free = 400m
200 free = 800m
The world record for 100 free is 46.91. The world record for 400m is 43.18. So around 3.73 seconds difference.
The world record for 200 free is 1:42.00, world record for 800m is 1:40.91. So only 1.09 seconds difference.
In doubling the distance, the swimmer has tired less.
400 free world record is 3:40.07. Whilst a mile is slightly more than double 800m at 1609.34m, the mile record is only 3:43.13. The swimmer has now caught and passed the runner as far as endurance goes!
So the swimmer is clearly outlasting the runner when it comes to distance also.
Does this mean the talent in middle distance running is weak?
To me, quite clearly swimmers are better endurance athletes.