Bahrain may not be as rich as Oman (alhtough that may not be a true statement but never mind) but it does have something that Oman lacks: The causway linking it to the Eastern Province.
On any given GF flight I would venture to guess that the majority of the high yield PAX are Eastern Province residents (expats and locals).
I don't see much of a hit on their revenue if they consolidate all their operations to Bahrain (which is esentialy the case already).