Why acorns dont form
I can't really see what is going on with your photos, since the images aren't sharp enough. But a possibility that comes to mind is that the acorns were coated with honeydew, a secretion from aphids, and stuck to the tree when they fell. Look at this thread:
There is no stickiness or visible aphids although i just saw ants on the immature acorns. The acorns hollow, harden and never fall off.
No wonder the ants were looking into the woody knits. So why do I have no acorns now that i know these are not acorns??
There are a number of reasons why acorn production is low. Some of these are weather and environmental related. Some have to do with the tree's cycle. Read here:
It maybe a cycle thing. I will watch the galls more in future. Thank you