yeah, but if your legs are stronger you should run faster

Actually you are wrong. For those who are distance runners it's actually true for short distance speed running and jumping, they do go hand-in-hand. Distance running involves high amounts of cardiac stress increasing the amount of endorphines generated within the nervous system and corresponding glands. It's also distinctly why distance runners have high stamina but physically inferior leg strength to athletes who rely on jumps and speed.

Compare this to athletes in gymnastics and track where developed leg strength allows for significantly higher leaps, jumps and faster sprint speed; the muscles utilized rely in similar areas (sprint running does utilize also portions of the upper body however) but is also a symbiotic issue; typically as runners increase their leg strength their jumping strength also increases which is why many of these athletes incorporate jumps with medicine balls in increase leg strength. This is also the particular reason long distance and marathon runners DO NOT overly develop their leg muscles: because it impedes their distance running by increasing overall weight loads over periods while also increasing the overall strain they place on their bone and tendon muscles.

In short: when you jump higher you typically run faster and vice versa. When you run at a higher speed for longer periods of time you don't typically have a faster sprint speed nor do you jump higher which has to do with different regions of muscles being developed and the extent they are developed.

I also only know this answer because I ended up making a transition a decade ago from hurdles runner, to track to marathon running which also meant less time in the weight room and more time running so I already had the answer before all of this. And if you like to disagree with the logic, show me one distance runner with developed legs? Yeah we're all chicken legs, the WHOLE LOT OF US!

hell most of the worlds strongmen are considered lumbering and slow they're not that fast; yet usai bolt is a amarr thrice damned twig in comparison; his descendants will definitely escape the first reclaiming.