The premiere running event in Southern California is the LA Marathon. Sand Diego has the Rock 'n Roll Marathon as the main event, but also hosts other events.
In Orange County (CA), the premiere event is next weekend, the OC Marathon.
http://www.ocmarathon.com/
This event has always been the big Kahuna of events, and held just south of Disneyland.
So yes, there has always been plenty of local races to take advantage of.
But the runDisney events attracted a lot of tourists (Similar to the Rock 'n Roll San Diego event), and RunAnaheim, a division of Visit Anaheim, the area's tourism marketing group, is trying to tap out of the area runners.
One key difference, since this is a "charity" race, California law will allow volunteers, unlike runDisney, which was forced to switch to a paid staff covering the course, and one of many reasons why rD left Anaheim.