MIRI's stated goal is more meta:

The Machine Intelligence Research Institute exists to ensure that the creation of smarter-than-human intelligence benefits society.

They are well aware of the dangers of creating a uFAI, and you can be certain they will be real careful before they push a button that have the slightest chance of launching the ultimate ending (good or bad). Even then, they may very well decide that "being real careful" is not enough.

Are there other organizations attempting to develop AIs to control the world?

It probably doesn't matter, as any uFAI is likely to emerge by mistake:

Anthropomorphic ideas of a “robot rebellion,” in which AIs spontaneously develop primate-like resentments of low tribal status, are the stuff of science fiction. The more plausible danger stems not from malice, but from the fact that human survival requires scarce resources: resources for which AIs may have other uses.

Many AIs will converge toward being optimizing systems, in the sense that, after self-modification, they will act to maximize some goal. For instance, AIs developed under evolutionary pressures would be selected for values that maximized reproductive fitness, and would prefer to allocate resources to reproduction rather than supporting humans.

Are there other organizations attempting to develop AIs to control the world? Is anyone else trying to build a benevolent dictator?

Is MIRI attempting to develop any sort of AI? I understood the current focus of its research to be the logic of Friendly AGI, i.e. given the ability to create a superintelligent entity, how do you build one that we would like to have created? This need not involve working on developing one.