Sean always writes interesting articles. I was talking to some music industry people about this a couple weeks ago. One of the problems is that some of these artists get signed on the strength of one song. A label guy sees a video on YouTube or TikTok, contacts the singer, and they put it out as a single. It becomes a big smash, but there was no plan for the follow-up. They look at what else the artist has in the can, and it doesn't compare with the big hit that got all the attention.
On the other hand, Sean mentions Bailey Zimmerman. In his case, I know there was a lot of competition to sign him, so that tells me he was ready with a follow-up. I saw him do a short show recently, and he already has a fan base who know all of his songs. His latest song is a follow-up to his debut #1. As he introduced it, he said it was already the biggest hit of his career. That surprised me, because "Fall In Love" got a ton of radio airplay on its way to #1. But the fans were primed and ready for his followup.
Another story I hear is that the debut hit is so big, that any follow-up gets lost in the shuffle. The fans are still stuck on the debut hit, and radio is still playing it as though it's a current. That prevents the follow-up from getting any traction. The label may have to go a couple singles before they come up with a song that can beat the debut hit.
Every situation is different. It's more of a music problem than a radio problem. Radio is just fine playing the first hit as recurrent. But it's up to the artist & label to build the foundation for a career rather than just one song.