Mainly, they didn't. Some applications fell out of use for want of capacity to implement, but it's for very good reason we don't say 'Dark Ages'. (Directly related, screw you, Petrarch.) More can always be said on this matter, commonplace as it is in the popular understanding; for the meantime, here are some previous posts for your attention:
In this old thread I myself and some others discuss this topic in broad terms, and there is a good deal of bibliography cited for further reading.