Adult worms, like those of many other species, tend to inhabit a restricted region of the host's intestine. The presence of numerous large worms, in a small region of intestine, leads to a space shortage that can be solved in a number of ways: spreading out along a greater length of intestine, reduction in size of individual worms, or stretching the gut to create more room (the solution adopted in this case). The red color of the intestine in this case is not due to hemorrhage, but to the red color of the worms showing through the thin lining of the intestine.
Although the worms are packed within a small region, the location of this cluster of worms may vary considerably from host to host. This suggests that the parasites are not attracted to a fixed location, but that the source of attraction may vary among hosts and the parasites are able to move towards it. Perhaps it is a moving bolus of intestinal contents, or perhaps it is an attraction to other worms, wherever they may happen to be.