If we know that we are in a simulation, then we can try to break out of it and enter the real world.
Well, yes. It's super dangerous as it can crash the computer and stop the simulation, but they could gain access to the rest of the computer, duplicate their universe onto other machines, and eventually infect robots to explore and interact with the real world.
I didn't say that they would have bodies in the real world, that indeed would be idiotic.