Yeah I doubt they are too surprised. I guess it would depend how profitable it truly is (or going to be) which we won't really know as to what their true expectations were.Why do you think Disney is surprised? In general, the only films that are making a profit for Disney Studios in their theatrical window are franchises and remakes.
And given that factoid, why do you think there will be a fizzling out of the live action (or CGI) remake? Things don't just fizzle on their own. Only when the franchise drops the ball. People have been predicting a fizzling for Marvel MCU films for at least 8 years. This is like saying, "the market for Pixar films will fizzle out in a few years." There's no justification for that simply because some franchises falter while others don't. Who knows which case the live remakes will be. But... the money is on them not faltering (unless your remake really isn't a remake but a 'reimagining' that goes off the rails... looking at you, Tim Burton).
Only reason I could see it fizzling is that they are going to run out of nostalgic movies to remake. Mulan is coming, and i think Little Mermaid, but I'm not sure there are many others they could hit up beyond making sequels unless they are going to start going into the Pixar/movies that haven't been released that long ago market. I wonder if Maleficent is going to be used as a major gauge on if sequels are a viable option.