Taylor Swift makes a lot of her money from being Taylor Swift (i.e., tours), per https://www.investopedia.com/taylor-swift-earnings-7373918:

> The 12-time Grammy Award winner made more than $780 million on the U.S. leg of the Eras Tour, according to an estimate by Forbes. The total ticket sales from Swift's 2023 Eras Tour could make her the highest-grossing female touring artist of all time, according to Billboard. The Eras Tour could gross over $1 billion, making concert history as the first billion-dollar tour, according to The Wall Street Journal.

J.K. Rowling doesn't have exclusive rights to her books, past the first couple. Lots of copyright-related suits (most?) are made by Warner Bros. She's fully capable of mobilising her fanbase (or, was, at least, before she went off on the deep end) to prevent or restrict what she considers misuse of the Harry Potter brand. (And, as you say, she doesn't need the money.)

Copyright isn't why Toby Fox need never go hungry. His work is trivial to pirate, he doesn't even bother enforcing copyright on his music; and yet he's probably a millionaire, with more works on the way.