If you look at the details, I would lay the blame on Ghemawat and Jeff Dean and their insistence on using C++ for everything. Nobody could argue against them, even VPs.
When YouTube joined Google, their engineers were shocked to find that Google engineers were writing 1000s of lines of server side C++ code, that could be accomplished in 100s of lines of python code. Which explained why YouTube was able to move a lot faster and pump out features, while Google video was struggling to keep up.
It was not the leetcode engineers, but Dean and Ghemawat insisting on C++ only on the server. Its still true today. Go might be making inroads now.
It was Google engineering that allowed YT to scale.