There could be any number of answer to why this is, but it’s only partially a matter of race and mostly a matter of individual characteristics.
A lot of the features that West African blacks are more predisposed to having aid more in top speed than acceleration. Narrow hips help keep rotational forces low and minimize long axis rotation (important for top speed, not accel). Long limbs relative to the body mean longer levers (more important for top speed). Higher white fiber content and stiffer tendons allow for lower ground contact times (essential at top speed, but not so much during accel). Muscle fiber distribution favoring the hips, hip flexors, and hamstrings aid in top speed and SE (quad development can make up during early accel). And psoas development (which is on average 3 times greater in blacks than in whites) is needed for efficient top speed running.
Now, all of the features listed above primarily play a role in top speed. It’s possible to have wide hips, short legs, short tendons, and a mixed fiber type and still have good acceleration. Since black athletes more commonly display positive characteristics, it would make sense that they would commonly exhibit greater top speed and SE.
Having said all of that, it’s perfectly possible for a white guy to have all of the same characteristics as Usain Bolt, but it’s unlikely (truth be told, it’s unlikely for a black guy to have those characteristics as well).
The reason we see less white sprinters is because West Africans more commonly exhibit the traits that make them great sprinters. And since Olympic sprinters are already 1 in 10,000,000 (or more), it’s just a matter of finding those with the right characteristics. What this may mean is that for every 4-5 black guys capable of going sub <10, there may only be 1 or 2 white guys, but they’re there none the less. Race says nothing about an individual’s abilities, only their individual characteristics do.
As for the relative success of white athletes in the 200M and 400M in comparison to the 100M, this could be a case of the really good white athletes actually having been located, or it could also relate back to genetics. I would personally assume that Mennea and Wariner could’ve done great the 100M (or 200M in Wariner’s case), but might have been steered away for one reason or another. Either way, their accomplishments show it’s not about race, it’s about finding athletes with the right characteristics.
It’s just that fewer white athletes exhibit them, so the search is a bit harder.