bmi rejected Shannon's approach for a service to LHR because the LHR slot was more valuable to them for other services. Market forces, nothing to do with Ryanair.
Aer Lingus pulled out in a hissy fit because they had to continue to operate their long haul through Shannon when they wanted to drop it completely. Nothing to do with Ryanair.
FlyBe pulled off the Shannon - BHX route long time before Ryanair set up the BHX base. Nothing to do with Ryanair.