We don't just have to believe them, we have to believe the messengers: Citadel and Griffin. Both are prolific liars and manipulators.

But assuming Griffin, Citadel, and Citadel's employees are telling the truth, that they are victimized more than they were before (with some nebulous definition of "before"), we also need to assume that they think they'd be safer in Miami and are eager to move.

You may be right that it's more than politics, but politics seems to be more than enough incentive for Griffin just by itself, and the other reasoning is not very plausible in the first place.