Sealer Reaction

Hi! I'm trying to figure out what happened on a wall shelf I was painting recently.

It was stained and sealed, so a washed it with hot soapy water. I painted 2 coats of the ultra matte paint shown in the photo. It has been sitting like that for a week.

Today, I distressed it with my sander. I wanted it to stay that way, so I brushed away the dust and applied a coat of clear sealer....and before I coated everything, it started bubbling and cracking! Any ideas as to what happened? So bummed...thought that project would be finished today, and it looks like it will need a lot more work to be presentable.