The 3D spectacular became the top grossing movie of all time on its initial release, replacing another James Cameron directed movie Titanic, which had been there for 10 years.
Avatar was also at the top for 10 years before being replaced by Avengers: Endgame which narrowly grossed more than the $2.78 Billion Avatar took with a $2.79 Billion global gross.
It was clear that all it was going to take was a successful re-release of the Avatar movie to reclaim the top, and in a period of time when studios are being cautious about releasing new movies why not release a film which has already made its money?
The real big winner here is Disney, they of course own the Marvel Universe movies for which Avengers: Endgame is one and since the 20th Century Fox acquisition in 2019/2020 they also own the Avatar franchise, so are Disney now going to re-release the Avengers movie?
James Cameron is currently working on 4 more Avatar movies and judging from this re-release the fan base is still there and hence the future for the franchise looks promising, maybe we'll get the first $3 Billion movie once the pandemic is out of the way?