There are degrees of unhappiness. There's no reason to assume a binary of loving everything about work or hating it so much that they'd be happier without it.

To be clear, this isn't intended as a criticism of your choices to step down from maintaining various projects; my point is that these choices are quite personal, and it's not always going to be obvious how to balance the tradeoffs. It's entirely possible that they are burnt out to the point that they might be happier in the long run if they did step down now, but it's also possible that they might be even more unhappy giving up something that they care a lot about and are willing to tolerate the less fun parts. I suspect you could provide a lot of valuable insight on these sorts of decisions given you experience, but even from having to make similar decisions for things with a tiny fraction of the exposure of the projects you've maintained, it's clear to me that there would need to be quite a lot more nuance in analyzing a situation like this, especially from the outside.