Although I agree with the general sentiment of this article- journalists gravitates towards their career not for the job itself. I think he's making a pure speculation on the "journalists have rich parents" point.

I think it might be something much simpler, like "journalists often can't find another job based on their english-adjacent degree; and the barrier to entry for journalism is very low".

Of course, when the barrier to entry is low- and most candidates are indistinguishable- you hire your friends; which inevitably leads to homogenization.