I'm going to guess this is the Satanic Temple responding to some other religious display being displayed inside the Iowa State Capitol.

This is what they do. They're not even "Satanists". They're really atheists who pretend to be "satanists" in order to put up this display, declaring that it is their religion, so they have the same rights as any other religion that displays religious items on federal property.

You won't see this from them unless there is some other religious iconography or material being displayed on state/federal property. It's their way of saying that the Religious Exemption Clause in the First Amendment is being violated.