I think it's also because there are now lots of colleges in the US that have almost no minimum academic requirements to get into and because of this, they also need to water-down the curriculum so they don't have high failure rates.
I'd go further and say that among the intellectual elite, having a degree is more based on whether or not your interests overlap with things that colleges have to offer than some default for very smart people. It is not the default now.
1939 was a radically different world and country from 2024.
In 1939, most Universities were there for the elite and the exceptional.
In 2024, most Universities are "High School 2: Away from Home".
The article basically says as much, but the headline really smells like it's trying to make the "people are getting dumber" case.