This is what I can say about the reason why Kenya didn't make it to the top list
Most of the questions of such websites require a certain set of skills set that is never taught in our universities but which should be taught. Most graduates in Kenya don't understand the meaning and/or significance of algorithm complexity analysis and/or some of the concepts tested in this competitions.
Taking my case as an example, my lesson on dynamic programming, a topic that is center stone is such competition and which is actually of great use in real life went as far as telling me how to multiply a chain of matrices and then telling me that the way I parenthesize the matrices changes the number of scala multiplications required to solve the whole problem. And that was the end. It wasn't until years after college that my feeling of lack of understanding lead me to investigate and read on such concepts into details.
Most Kenyan students don't know why quick sort is O(nlogn) in average case and O(n^2) in worst case and usually end up memorizing this time complexities since they know in the exam they are the only ones that will be asked. When learning mathematics, the mathematics teacher as good enough to proof to me that the sum of the first n integers is (n2+n)/2 but my algorithms lecturer never mentioned that the reason O(n^2) algorithms are O(n^2) is because for each iteration they take n then n-1 all the way to zero (comparisons/swaps/the operation of interest) and the total number of operations is the sum of the first n integers.
I know some might say that lecturer is only supposed to give you guidance, but I have seen lecturers from MIT online and they do emphasize and show all these. The best time to learn these things are in campus, not when you are out in the field trying to develop systems and then stumbling upon problems.