It must have been the stropping, IMO.

As Jimmy said, the death-blow was the subsequent honing - maybe you could have brought the edge back on the leather up to that point (if you didn't roll it, that is).

Just FYI, I usually do 30 on linen and 50 on leather. Linen is quite coarse - more abrasive than cotton, much more abrasive than leather.

Regards,
Neil