They don't need to. They do need to keep the stock price up just long enough to cash out and leave a sucker holding the bag.
Edit: not that I'm against paying mods, I support that. But replacing enthusiast mods with paid mods, I doubt that'll be adequate.
There's a bit in Predictably Irrational by Daniel Ariely where he talks about social compensation vs. market compensation (I could be remembering the terms wrong). He asks how poorly it would go if you went to Thanksgiving dinner with your grandmother, and after eating the amazing spread you handed her a $20 and said, "That's for the great food, gran, it was amazing!"
Gets rid of a nuisance relatively easy, but degrades the quality. But reddit doesn't seem to care much about quality for the last years so.