that's probably because this was made on Flash.
Newgrounds has an alternate Flash player you can use.
There also Ruffle, but I'm not quite sure about the reliability of that one...
Granted, I haven't downloaded either of them because I'm a coward who needs the permissions of the local expert (that being my Grandpa, who IS trained in cyber security so he's actually pretty good at telling scrap apart) before doing stuff like that.
No, I'm not telling you his name.