judging by the shinyness of the photos, your bike has old steel rims
the modern tire is rated to 90, but the old rims are only rated to 65
you have to go by the Lowest rating for things to work together
as for why didn't they blow out immediatly after inflating but only after 2hours when you rode it? because you weren't riding it yet; weight of rider and the action of rolling was the last straw.
stay at 65psi
it sucks, i know, they feel flat all the time
thats why the design is considered obsolete
you can either live with it or change to modern aluminum hooked rims designed to take higher pressure