Originally, The One and Only Ivan was going to be a theatrical release, but with the ongoing scheduling issues that have popped up as a result of theater closures, the decision was made to move the film to Disney+.
The One and Only Ivan isn’t a massive brand or franchise.
While the movie certainly could have done well at the box office, it was never going to put up Marvel or Star Wars numbers.
It might, however, get all the people who just subscribed to Disney+ for a month to watch Hamilton to hang around for a second month to check out the next new film.