Religion is filled with all kinds of absurdities. People string a bunch of words together and pretend they actually understand what they’re saying. But because there is no objective test for whether they really understand what they’re talking about, they tend to get away with saying all kinds of things.
It’s because religious concepts are generally metaphysical concepts, “metaphysics” being defined as “a study of what is outside objective experience” (http://www.merriam-webster.com/dictionary/metaphysics).
So, generally speaking, people are free to make up any religion they want, because there is no objective way of knowing whether a religious claim is true or false. Even if they don’t make up a religion from scratch, people are free to interpret/misinterpret any existing religion any way they want.