npm has to deal with scale: it's now the largest programming language package manager, and most project dependency trees have exploded in size as a result. Optimizing that led to yarn and to npm@5.

npm has to deal with scale because every single npm install goes to npm instead of a local cache of certain versions.

Bundler led to yarn. The JS community should start looking what other ecosystems do and have done (right and wrong).

Such a waste of time these past 20 years and it happens over and over.

I could be incorrect, but I don't believe Bundler was the first to lock and manage dependencies? I seem to recall using such tools before 2010. This isn't to take away from your main point by any stretch; only recently has JavaScript gone from "downright terrible" to "tolerable" and most of it is through doing what others already did, better, many years before. It still feels like a lot of the community doesn't have sufficient exposure to stuff outside their closure and people who work with that community's stuff are the worse for it.

This statement is false and has been since the very first work done on the npm cli. npm has, in every version of it that has ever existed, since before there was even a package registry, installed preferentially from its local cache of packages where possible.