Gadot did pull in a lot of money for the first WW film. It was mainly China that helped catapult Aquaman over Wonder Woman at the box office, a marketplace that has proven to be very notorious and unreliable recently with no Marvel movies (+ The Suicide Squad) getting released in the country in 2021. When it came to the US box office, Diana defeated Arthur thoroughly.
If the rumors are to be believed, the real reason Batfleck and Superman are being phased out is because Affleck is done (also why the Matt Reeves movie went for a total Bat reboot), and Cavill apparently started making demands similar to what a Robert Downey Jr. over at Marvel would make in terms of pay. Only thing is, Cavill hasn't proven that his Superman is a draw at the level of what RDJ's Iron Man was. I can see why WB didn't want to make that gamble and decided to go for a cheaper alternative with Supergirl and some alternate universe takes on Superman.