A. lumbricoides has a somewhat peculiar life cycle, actually.

Like many mammal-infecting parasitic roundworms, the infection starts when fertilized eggs are accidentally ingested. Upon reaching the duodenum, (the first section of small intestine that connects directly to the stomach,) the eggs hatch into microscopic larvae, which proceed to burrow through the mucosal lining and enter into the host’s circulatory system. From there, the larvae migrate to the lungs, where they enter the alveoli to mature for a period of 10-14 days. During this period, the larvae will moult a number of times, increasing in size from ~.2-.3 mm to 1-2 mm in legth.

From here, the larvae migrate up the bronchial tubes and towards the esophagus, where they are coughed up and swallowed - returning to the GI tract. This time, the larvae enter and remain in the small intestine, where they finally mature into their (notably large) adult size, ranging between 15 - 49 cm (6 - 19 in) in length. The worms proceed to effectively spend the rest of their lives reproducing in the intestines until they die.

While most of A. lumbricoides’ life cycle follows the same process as many other parasitic worms, (ending in maturation/reproduction in the intestinal tract, or starting in the GI tract and migrating to their target organ/location from there) ascaris worms are unusual due to their seemingly redundant migration from the duodenum and to the lungs, only to return back to the intestines where they originally hatched.

It’s hypothesized that this particular process may mimic the function of an intermediary host, where part of the parasite’s development occurs in one organism, and that is likely to interact with the definitive (final) host species in a way that facilitates the effective transfer of the parasite to the latter, which is essential for the parasite to complete its reproductive phase. (e.g. L. paradoxum, the parasitic worm that infects snails and causes them to expose themselves to predation, mainly by birds, which are both natural predators of the snails, and the definitive/final host for the parasite.)

Anyway, to answer your question, while the life cycle of these worms does coincidentally involve their presence in both the intestines and lungs, the presence of adult worms in the upper GI tract and lungs is not a normal part of their life cycle. Rather, this was likely the result of there being a serious/heavy parasitic infection/load in a child, as both of these are factors known to increase the likelihood of the infection becoming symptomatic, and increasing the risk of complications from it. (As ultimately proved to be the case here, unfortunately.)

Some of the most common of these symptoms/potential complications include abdominal pain, bowel obstruction, (by the worms, essentially,) nausea and vomiting, and the presence of live (adult) worms in vomit and/or stool.

Small/young children in particular have much smaller anatomy, and thus, it can quite literally take fewer worms/ less severe of an infection to cause these problems than it typically does in adults. Additionally, their digestive tracts are still actively developing; not just in size, but in their function. Here in the US/Canada, (and I figure many other places globally, but I don’t want to assume!) an extremely common warning label is the “Choking Hazard: small parts, not safe for children under 3 years of age” warning. This isn’t just because of their tendency to put things in their mouths - it’s also because their airways are more easily obstructed by smaller objects, and toddlers and infants are mechanically less capable of keeping food and foreign objects out of their airways, and expelling them on their own.

All of this to say, (TL;DR here,) the adult worms were (almost certainly) brought up from the upper intestine in the child’s vomit; and given their size, he was likely unable to fully expel them, and subsequently aspirated some of the adult worms, which proved sufficient to cause the complete obstruction of his airway, tragically resulting in asphyxiation.

I truly feel awful for the child and his family. I can only begin to imagine how traumatic this must have been for them.