[vanderZwan]

Insertion sort is known to be the fastest option for small ranges, which is why it often is the sorting option hybrid sorts switch to for that case (like when the partitions in quicksort or merge sort are small enough).

AFAIK, this is mainly because even though it is expected O(n²), it has a really tiny overhead because insertion sort is incredibly simple, so for small enough n it wins. However, being very cache-friendly is also part of it (it's a linear search over the array).

IIRC some people found similar results for bubble sort.

[steerablesafe]

It's both cache-friendly and its branches are easy to predict.