There had also been whispers of unpredictable behaviour on the set of the latest Pirates of the Caribbean film — later extensively fleshed out by crew members — that suggested the 55-year-old actor's craft was not as laser-focused as it might have been.
Even at that relatively late stage in mid-2016, Depp could have been easily and quietly Kevin Spaceyed out of the picture. Nothing about the role of Grindelwald — a proto-fascist agitator whipping up anti-muggle sentiment in the Thirties — suggested Depp was the only man who could play him.
Also, no one knew he was actually in it. In a statement, Rowling admitted she and the director David Yates had discussed recasting, but said that based on their understanding of the circumstances, they were "not only comfortable sticking with our original casting, but genuinely happy to have Johnny playing a major character in the movies", before adding, a little spikily, that "conscience isn't governable by committee".
In other words, a reckoning had been made at Warner Bros, and had concluded that Depp would remain a viable star and a net asset until 2024 at least.
To a critic who has spent the past eight years watching Depp floundering professionally, while his PR liability rating creeps ever higher — well, that seems like an odd call indeed.
There is no mystery around why Depp should want to secure another prominent, and therefore well-paid, recurring role. A legal spat with his former business managers last year shed light on a lavish lifestyle that reportedly cost the actor an average of US$2 million ($2.93m) per month, including a wine tab of US$30,000 and a lump-sum payment to fire his late friend Hunter S Thompson's ashes into space from a cannon.
"It's insulting to say that I spent US$30,000 on wine, because it was far more," he clarified in a Rolling Stone interview, in which he also estimated the cost of Thompson's extraterrestrial committal at US$5m.
His personal spending was presumably only able to hit such heights thanks to the Pirates franchise, which transformed Depp from Gen X heart-throb to global megastar in 2003. And even last year, the middlingly reviewed fifth outing was able to scare up more than US$1.1 billion worldwide.
But with Disney reportedly sounding out a reboot, Depp's buccaneering days are likely numbered.
So what else has the present decade yielded? Half-formed vanity projects (The Rum Diary), wacko-goth diminishing returns (Dark Shadows, Alice Through the Looking Glass), glorified cameos (Into the Woods, Lucky Them), corny throwbacks (The Tourist) and outright abominations (Mortdecai).
There were also two notable box-office bombs, The Lone Ranger and Transcendence, both heavily marketed on Depp's involvement. Neither is as bad as you've heard, but with combined losses of around US$300m, they suggest the public appetite for Depp is conditional on galleons and Jolly Rogers.
Next came an attempt to move back on to the Oscars' radar with the 2015 true-crime saga Black Mass. But his lead performance as the Boston gangster "Whitey" Bulger was buried under unconvincing and unnecessary prosthetics that left Depp looking as if he was trying to act though a chapatti.
Then there was to be a remake of The Invisible Man — part of a proposed "Dark Universe" of films at Universal, in which classic monsters would be revived for the blockbuster age.
But after a Tom Cruise-led version of The Mummy failed to excite audiences last summer, the Dark Universe was quietly snuffed out.
Another true-crime thriller, City of Lies, in which Depp plays a detective investigating the 1997 murder of the hip-hop star Biggie Smalls, was supposed to be released in September. But it was pulled from schedules and remains in limbo, after the film's location manager filed a lawsuit alleging Depp had physically assaulted him on set, which Depp denies.
Perhaps Rowling and Warner Bros are banking on international audiences just not caring that much about Depp's personal or professional travails. Even as the Pirates films faded in the West, the last one did gangbusters in China.
Perhaps there is also a hope that Depp has one more iconic performance in him. As for Depp, it seems unlikely that he is about to give the world his archetypal evil genius in episodes two to five of something called Fantastic Beasts. But perhaps he will discover a corner of his jungle that remains unscorched.