So the simple explanation might be that the pulleys are old and are failing. Images below show the pulley I replaced and the pulley that was thrown (Just like the other pulley that I replaced) You will see the bolt/shaft for the pulley is still in place and is ribbed. The bearing of the pulley is free but is smooth. It is coming off the shaft.
On the new pulley, the black spacer that you see on the shaft, is attached to the pulley. I am wondering if this is just old and failing. I want to make sure I am not doing something else wrong before I spend more money.