You might be thinking that he just wanted to wander, look at the attractions and just kinda hangout in the happiest place on earth. Eh, well no, actually he was there to steal valuables and resell them when the park reopened.
When he was apprehended, he admitted to just being there to try and steal some items to make some money off of it. He had tried to break into the park via the Avengers Campus which is currently under construction.
While the thought of wandering around a completely shut down Disney World sounds hauntingly cool (like seriously, Disney if you read this I also do photography and that sounds awesome.) It’s still not a very classy act to try and take advantage of a crisis.