Who cares if they are Protestant and who knows or cares what the founders would have thought about it?
If should matter to pretty much everyone. Protestants started the country, were the solid majority up until just a few years ago, and the basis for the Constitution and common law are the result of Protestant initiatives under the Reformation.
Are you really here to tell me that Freedom of Religion - i.e., no established State religion - is the result of a Papal Bull?
Sorry, but a court is not a computer. They don’t simply process information, establish links, and promulgate a conclusion based on mechanistic interactions. Principals and history, personal experience comes to bear. Why would the citizenry want to be judged by people who don’t have a common bond with them?
So that’s why you should care. A lot.