How Cavill was Played by The Rock
Firstly, Cavill was removed from the Superman role in 2017 after Justice League. The New ATT Regime and Cavill could never agree to terms on a deal and eventually WB just decided to move on. (that's Hollywood baby!)
Hamada didn't "secretly" hire Gunn to write a Superman movie. He was building a DC universe and needed a Superman and WB/Cavill couldn't agree to terms. So he kept doing his job until he was removed from it. Just because it wasn't made public (which there were plenty of rumors that Gunn was doing it) doesn't mean it was secret. Dwayne Johnson and Hiram Garcia are the MAIN reason things played out as they did.
They knew that Zaslav was searching for someone new to replace Walter Hamada and head the DC Brand and eventual DC Studios. They pushed hard to get Cavill in Black Adam even convincing WB Producers Abdy and DeLuca to invest money in shooting scenes with Henry (Cavill) for The Flash and even Shazam! Fury of the Gods.
This was Dwayne Johnson and his Seven Bucks production company's way of trying to strong arm their way into the position that Zaslav was looking to fill.
According to a report from The Wrap, the plan was to have Hiram Garcia be the face and head of DC while Seven Bucks production would be the production house behind him and the films.
Unfortunately, The Fan reception was poor with Cavill's return and Black Adam underperformed both financially and critically with the fans.
Those Hashtags calling for Cavill's return were proven to be Snyderverse hashtags in disguise.
While the belief was people simply wanted Cavill back as Superman... the truth was they only wanted Snyder's version of Cavill's Superman back. Thus the reception of his return went from excitement to bewilderment and then anger.
Zaslav did the only thing he could do. With Dwayne Johnson's Black Adam failing and him and his production company wanting to continue with the core characters from a FAILING Franchise and Brand... He had to move on from them and get someone else in place that would be willing to start anew and reinvigorate the brand.
Peter Safran has had plenty of success over the years as a producer. Sure he played a role as Producer in the DCEU... But to this point 3 of the 5 films he has been involved with have either been financially successful, critically acclaimed or both. The problem here is Safran isn't a massively creative mind that can build a Cinematic universe.
Knowing how great James Gunn handled the GOTG, their relationship on The Suicide Squad, as well with how Gunn was originally going to run the COSMIC UNIVERSE for Marvel Studios... He was a perfect choice to bring in and help build the Franchise.
Henry Cavill would go on to fire his management team after this ordeal. It's apparent now that he was played and used by Dwayne Johnson and his team in their attempts to take control of the DC IP. Promises were made that were never able to be fulfilled and Cavill's team let him walk right into it. (Not surprising since his management team at the time was also Johnson's).
The Divided fandom though struggled with this. While your everyday DC Fan was excited at the possibilities, the SnyderVerse side (which is divided in its own right) began to blame Gunn for all the shortcomings of the DCEU, despite him being hired specifically to distance the brand from those same failures.
Instead of the DC fans coming together and believing that this is the best course for the brand. They continue to fight amongst themselves while one side tries to push lies and toxicity towards Gunn and DC Studios and the other simply wants to take the wait and see approach.
No worries though, a Brand New Era of DC Films is about to begin!
