[smaudet]

Maintainers often change (leave/die/hired out/new job).

What one maintainer knew and understood, is often fairy dust/spaghetti to another.

[arp242]

Looks like there was quite a bit of attrition in the early 2010s after Oracle stopped developing their commercial version (and presumably stopped hiring the developers). There's also been people who stuck around, but this was probably a pretty big knowledge drain.

See e.g. https://gitstats.arp242.net/LibreOffice/

[apitman]

And skill level can vary vastly from one maintainer to the next. I suspect this will become a more and more significant problem as time goes on.