Again, you are missing the point that nobody joins Spotify for the Podcasts, it's rather irrelevant that he's more popular, people don't join for Rogan
Sure you can listen to Rogan without subscribing for which Spotify gets advertising revenue but Spotify earns minute amounts of money from their advertising compared to their subscriptions and the subscriptions are generated through the music not the podcasts
I also think you're underestimating how popular Neil Young is too, the documentary of the making of his latest album has 350K plus views on Youtube in 6 days, the lead song from the album has double that in under a month
There's absolutely no way Rogan earns Spotify the money they are paying him, they are paying him the money to keep his product exclusive to them and that money is coming from the music artists they quite literally fleece
Neil Young doesn't need the $20k a month he earns from streaming on Spotify, he doesn't even need Spotify to promote his music, leaving Spotify will do nothing to his fanbase, they aren't going anywhere
Why should Neil Young partly fund Rogan's anti-vax / pro-fascist podcasts? He's decided he isn't going to any more