The leather was fine. The part between the rubber sole and the leather shoe (I think it is called midsole?) just disintegrated.

The were stored in my shoe rack. I wouldn’t say that it is particularly humid there but it would be warm-ish (depending on the weather).

I wasn’t particularly shocked by this since they were simply lying around for that long. Maybe active use would have extended their life a bit more.

But maybe I can give them to someone that can add a new midsole so that they can be used again.