What if you have to use eminent domain to build the wall? Trump would build the wall while the rest would make speeches.
Building the wall (which Cruz will do as well) is a legitimate government function. It's part and parcel of protecting and defending our border. That puts it in the same bracket as a road, a school, or a hospital.
What went on in Kelo and in Atlantic City was simply the transfer of wealth in the form of property from poor and middle-class people for the benefit of private interests -- generally wealthy ones, at that.