I've had similar failures. You just never know. Some saddles get so dried out. I had a Brooks Pro from the early 70's, from a Gitane TDF I bought last year, that was never reslly broken in. Put proofhide on it and rode it for a few hundred miles. The saddle just started developing cracks all over it. Weirdest thing I ever saw. Really upsetting as it seemed to be a perfect saddle.

When I get a dried out saddle now, I treat with mink oil and put the saddle in a plastic bag. Let it sit for several weeks and then give it a go. I did this to a 1950's Follis branded saddle that I thought had little hope, but it rehydrated and is holding up well.