Existing paint peeling
I began the weekend hoping to paint our bedroom, and per the usual, it ended up being way more work than I could have imagined. When we began prepping the surface, we noticed that the old paint was coming off the drywall in sheets except for the areas where the paint was over drywall spackle (i.e. areas of drywall screws and drywall edges). Since it was so hard to remove it in those areas, we decided to stop removing the existing paint and just use spackle to blend in the edges. Well, when we went to prime the walls, it caused the old paint to just bubble up and come right off. So, we went through the 2 days process of removing all the old paint off the walls, the room now looks like it was just freshly drywalled.
We figured we had to remove it all since the old paint was textured and would have been impossible to match if we tried to do new texture.
My question: Why was the paint so easy to peel and should we do the same thing with the remainder of our bedrooms? Could it be sanded instead?
The home was build/first painted in 1978 with white paint and sand texturing, and was then repainted since then by previous owners.
Thanks in advance.