I imagine it's highly likely the Jordanians have seen the number of tourists visiting Morocco and Israel and decided they want a piece of the action. Excluding APD, some days fares are about 40 pounds one way for a 5 hour flight - must be a big chunk of subsidy involved somewhere...
Ryanair and Norwegian are also starting flights to Aqaba from elsewhere in Europe on almost the same date as Easyjet which seems a bit of a coincidence