Eh, Scarecrow is bigger and more popular than Hush or Hugo Strange.
Scarecrow also had the coolest fights in the games so far too. There will be secret plots and likely a bigger villain behind it all too so no worries, Ras will likely be back too since his body disappeared after you defeat him in City.
The selling point of this game will be it being a finale and being able to drive around in the batmobile. Imagine if they expand the city and make this a GTA Batman.