Note that this isn't exclusive to FOSS, but it's just more transparent.
Over the last decade I've seen my work retire and replace with something not quite the same about 3 times now, owing mainly to some lead retiring and the replacement getting to finally throw it all away like he thought should have been done years ago.
But even in the more mundane case of things continue, it happens all the time in long standing corporate projects. Sometimes you can catch a whiff of a strong shift in direction (e.g. Windows 8 went hard on UWP and actively discouraged development using any of the long standing interfaces that Windows applications were traditionally built on). An announcing of retiring doesn't mean anything will necessarily change at all, or if it changes in a bad way there may be course correction.
It's gotta change to true community, where we lift each other up, looking to the future, readying others to take our mantle when we retire. That's the only way FOSS will thrive and have a chance to compete with corpos.
A number of them have written about their reasons- I can't speak for the maintainer this article is about but the general sentiment I've seen from the ones I've been hearing about is that the culture around kernel development is dogwater. Lots of it surrounding refusal to make any space for R4L and shitting on devs working on it, but then also spinning out of that are maintainers likening their quality control responsibilities to being "the thin blue line".