What is happening to this spider?
It is hard to say for certain, but the insect hanging from the spider looks like it may be a member of the family Elateridae, commonly known as a "click beetle". As far as I know, they're harmless and no threat to a spider.

The close binding of the legs with silk suggest that the click beetle(if that is indeed what the insect is) may have been a meal prior to the spider's death, or packaged for later consumption.

Given the amount of debris in the webbing surrounding the spider's corpse, including some pieces of some sort of grass leaves, it seems likely that the webbing become tangled during or after the spider's death.  The placement of the click beetle is likely coincidental, although I suppose it is possible, given the positioning, the size of the click beetle, and what we can conjecture would be the size of the wound if that black material is seepage from a wound on the spider's abdomen, that some force actually punctured the spider's abdomen with the body of the click beetle.