My take from the article is that they're poor because the stupid ones went to college and 1) the increased demand increased college costs 2) amassed more college loan debt than previously "normal". From there I surmise that the stupid ones got useless degrees at a premium cost and can't get jobs with salaries to cover their stupidity.
Government guaranteed student loans making access to money easy is what drove college prices through the roof. Colleges like any other business charge what the market will bear. Students could "afford more" so they paid more - with a simple signature on the dotted line.
That is exactly what happened to the real estate market around 2004. Same cause and will have the same result for colleges.
Regarding spending, too many young people think they're smart because they can look up a complex fact on the Internet. What is missing is the ability to apply those facts in a useful way.
They have high monthly expenses just maintaining the latest smart phone and data/streaming services.
And then social media consumes a vast amount of their time that could have been applied to learning skills that will have a return down the road. The more they build their social media persona for the gratification of "friends" the more they get behind skill wise and the harder it is to catch up.