It speaks to the state of software engineering that people are complaining about file length, instead of something meaningful like cyclomatic complexity.
A 10k single line program can be easier to understand and better organized than an overly abstracted mess strewn across multiple files, but which checks all the "best practice" checkboxes.
Do you think the people who wrote this were measuring cyclomatic complexity? Obviously you can have >10k LOC file that is well-maintained and useful.. but there's ample evidence in the post that this was _not_ one of those, but a machine held together by duct tape, spit, and hope.
A 10k single line program can be easier to understand and better organized than an overly abstracted mess strewn across multiple files, but which checks all the "best practice" checkboxes.