Why Linux development happens on mailing list instead of Git?

Linux kernel development happens on Git. In fact, Git was created for the Linux kernel. Maybe instead of Git you mean GitHub? I can't find a link now, but if I remember right there was a brief period when Linux kernel development had to move to GitHub. Maybe when kernel.org got hacked? Linus Torvalds didn't like the way that GitHub formatted merge commits [1] (from a later date, but I think it was the same issue).

[1] https://lore.kernel.org/lkml/CAHk-=wjbtip559HcMG9VQLGPmkurh5...

Instead of Git? Git is just a version control system & it doesn’t dictate the system for communication + review.

Greg KH has talked about this on multiple occasions. The sheer number of developers contributing to the Linux kernel makes anything other than a plaintext email-based workflow impossible.

Assuming you mean GitLab/GitHub, it's mostly one reason: the number of trees and developers makes a single repository unworkable, and neither GitLab nor GitHub have tools to manage pull requests that have to be shared and reviewed across multiple repositories. With email you just Cc multiple mailing lists.

In addition, email is much easier to search and look at after the fact than a website. Especially with GitHub I have seen "these commits do not exist anywhere" errors way too often.

Related to this, email is easier to mirror. This causes a very problematic lock-in due to how much content is archived on the git forge that you've chosen.

Git and LKML predate GitHub, and the kernel was the reason git was born (Torvalds was unhappy with other devecentralized version control software).

Anyway, everything wondered where "Pull Requests" come from? Literally an E-Mail saying "please pull my branch ... at ....". Git has special tools to create and apply mails.

GitHub copied most of the LKML/kernel development flow and turned it I to a web UI. That's nice, but the text workflow is often faster and easier. And it works. And it is decentralized (a key requirement).

So yes. It is not broken. And GitHub would break the decentralized nature to some extent.