It appears that before the reins were passed onto James Gunn and Peter Safran, David Zaslav, Warner Bros. Discovery's CEO, believed that The Rock was the man to lead the comic book universe into its new age.
This comes from an in-depth Wall Street Journal report, which looks at both how we got to the current setup for the DCU and what's next for James Gunn's master plan. According to the report, The Rock was considered to be the person to lead the new DCU, with talks in place until Black Adam flopped.
Following the box office bomb of the film that was The Rock's baby, it appeared that DC wasn't going to thrive with Dwayne Johnson in charge, and instead the reset button was pressed. Black Adam did seem to hint at a new future for the DCU, with Henry Cavill's Superman making a welcome return in the end credits, but knowing The Rock, it's likely the D in DCU would have stood for Dwayne, with Black Adam being a much bigger player than his character should have been.