I remember reading them back in the early 90s (Robin Hood: Prince of Thieves, Far and Away, Back to the Future). They don’t seem to be a thing anymore (or am I just not noticing them).
As an aside I remember liking them but I was a preteen at the time so maybe they were terrible and I just liked the movies.
Just because a movie was based on a book, that’s apparently no bar to adapting it back to a book again. This Stack Overflow question lists Blade Runner, Planet of the Apes, V for Vendetta, Bram Stoker’s Dracula, The Wicker Man and many others.
But as of yet no Oppenheimer junior novelization appears to be forthcoming…
Thinking of how there was a licensed board game based on the movie Battleship, which is, of course, based on the board game.
Also a board game based on The Queen’s Gambit from Netflix. I don’t if that was just chess, or had some relevant metagame?
I remember noticing a few of those when I was a kid. I think most of the Disney movies that were based on fairy tales then got a novelisation a lot longer than the original story.