Rental car prices are all over the place the past couple years. If you find a reasonable deal far in advance, book it (not prepay, of course), and then continue to monitor prices. Sometimes you'll find something cheaper and you can book the cheaper and then cancel. Sometimes you got lucky with the first reservation and you don't find something cheaper. It's possible that indirectly
Epic Universe is causing a bit more demand and could be a small part of the price increase. But most of the time there doesn't seem to be an obvious reason, at least in our experience.