Islam was never the last religion to come about?

I had to stop at your first sentence, since it was in error. Even if Abraham were real, it is wrong to claim him as the founder of all religion. Religion has existed in some form or another for many thousands of years, and stretches far back into prehistory. Your Abraham character, if real, would have lived as recently as the 3rd or 2nd millennium before the common era. (I'm being kind to the biblical chronology here.) Religion can be inferred from artifacts that go back at least another 10,000 years, some would say another 100,000 years. So, your premise is so fatally flawed, I didn't bother to read the rest of your post.