Does anyone know why they used bubblesort in the first place? It is known for its bad performance, so what other factors came into play? Number of ops, maybe?
According to the Twitter thread linked, at the beginning there were only 30 items, so using bubblesort didn't matter. The number of items has since grown to a thousand.
For 30 items bubblesort might very well have been faster than mergesort.
Bubble/selection sort with early exit can win outright on big lists if they're already almost in order. Textbook example years ago was cheque numbers which mostly are presented in order.