Unfortunate for you but good to know.
Before I coated my garage floor I always kept the bike in a chock, usually a Condor. Never gave any thought for a tire letting go and allowing a slow tip over.
It gave out right where the chock was pushing on the tire. If dry rot, age, weak spot, whatever happened where that contact had been for a couple months I'm definitely assuming the pressure against the tire played a role.
Oh well....
The new tires are for front and back. Some nice Avons with the reinforcement to make them an even better choice for a bagger. When they got here I looked (duh...!) and the rear was dated two months ago. The front, however, is a little over a year old. That's fine. If I'm still riding this bike in my mid 70s with the same tires on it I'll deserve having to have bought some more!