At my last company I cut 8k lines from a 10k component and fixed every major bug in the process. It wasn't "dead" per se, but if you start by cleaning up one little bad abstraction then that opens opportunities for the next one and the one after that till eventually all you're left with is software which actually does what it's supposed to.

That hasn't been a unique experience either -- quite the opposite. Codebases bloat over time. The only thing astonishing to me is that in something as large as Bun they only found 11k lines.