Major medical emergency or death of spouse are primary causes for homelessness, as cited in the article.
This may be the case. Were you quoting the article when you posted and bolded the part where it reads 'These individuals pointed to a major event, like the death of a spouse or a medical emergency, as the trigger.' If so, I don't see where this suggests that it is the primary cause.
Most households today (58%) are dual income. If this is correct, why would the death of one spouse result in homelessness? Do these folks not have life insurance to provide for their families or their spouse? Medical emergencies are costly when you don't have medical insurance. Long term chronic illnesses are a drain on finances.
For example, my wife was chronically ill for decades prior to passing. Medical copays were a major expense for us. The last couple of years her medical copays were about $10 K a year even though she was on Medicare, and she was also covered by my employer provided health insurance. And I am not homeless.
Sure, there are some folks who have bad luck. The trick is to plan for these kinds of events rather than assume they will never happen.
Of all the people I know and that numbers in the hundreds, the only person who became homeless is an aunt. She never worked; her husband left her after many years of marriage. She was schizophrenic and therefore was on SSDI and Medicare, plus she lived in a subsidized single apartment in Venice Beach, CA. One day she simply left her apartment because she chose to be homeless, for reasons having to do with her illness.
Very often when someone is homeless, there is more to the story than they share. Far too often folks do not take responsibility. Many folks cannot admit that it is their choices which caused their unfortunate situation. Worse, they believe it is someone else's fault.