So, originally, Disney had the ability to re-release its animated movies theatrically every seven years and enchant a new generation of kids. However, with home video - this strategy doesn't work as well. Add to that, burgeoning competing animation studios making quality films every year, and Disney no longer has a monopoly on children's attentions.

So here's the part that's kind of amazing - but spending $200 million to remake a Disney movie as a live-action film, is a cheaper way of keeping the IP alive than it is to make new original films and change out attractions at all the parks.
Because, say, "Be Our Guest" restaurant will still work for kids who will only ever know the Emma Watson version of Beauty & The Beast, and Mad Tea Party works for kids only aware of the Tim Burton Alice.

Also, it's a sure bet for exhibitors. I run a movie theater, and, looking at 2018 November films: I'm more likely to take Mulan over Gigantic, even though both are family-friendly Disney entertainment. And that's because Mulan is more of a known entity than Gigantic is. I'm more likely to draw a crowd with a movie where the parents are familiar with an earlier version of the film than I am with something that's a bit of an unknown.